35Custards, creams and frozen desserts

Custards, creams, dessert sauces and frozen desserts are built from the same few things: eggs, milk or cream, and sugar. Heat sets the eggs and turns a thin liquid into a pourable sauce or a firm gel. Cold turns a sweet base into ice cream or sherbet. How eggs set is in see chapter 7: Eggs, and how to choose and handle eggs is in see chapter 15: Choosing the egg: grade, size and freshness.

Every one of these desserts carries a risk. Milk, eggs and anything made from them are potentially hazardous foods (PHFs), and so are pastries filled with cream. A PHF lets disease-causing bacteria grow if it is left warm, so each step below comes with its safe temperature.

35.1 Custards and puddings

What a custard is

The word pudding covers many dishes, some of them savory, such as blood sausage. The puddings in the pastry kitchen are custards: milk or cream, sugar and eggs, served as dessert. They come in two families. A stirred custard cooks on top of the stove and is kept moving until it thickens. A baked custard cooks in the oven without stirring until it is firm.

In both, the egg proteins set, or coagulate, and that thickens the liquid. Stirring breaks the set as it forms, so a stirred custard ends up as a sol, a thick liquid that pours. Left alone in the oven, the same mix sets into a gel that you can cut. see chapter 7: Proteins set: coagulation

Safe heat, and too much heat

A food mixture that contains eggs or milk must reach an internal temperature of 74°C (165°F) and stay there for at least 15 seconds. That is the floor for every custard below.

There is a ceiling too, at 185°F: hotter than that and the egg proteins curdle. A stirred custard is done when it coats a metal spoon, at 82–84°C for a mix with two eggs and 77–79°C for a mix with three. Both sit above the safe floor and below the ceiling, so the working window for a custard is narrow.

Stirred custards

Several desserts are cooked on the stove and stirred until thick. Once thick, they can go into a pan, be covered and be chilled.

• Crème anglaise: a stirred custard sauce flavored with vanilla.
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• Pastry cream: thickened with both egg and cornstarch, which makes it thicker and much more stable.
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• Cream pudding: like pastry cream with less starch. It takes flavors well and suits custard pie fillings.
• Blancmange: set with cornstarch alone, no egg. How much starch you use decides whether it is poured or molded.
• Panna cotta: set with gelatin. Heat the milk and cream, sweeten them, then melt soaked (bloomed) gelatin in the hot liquid. Pour into molds and chill until set.
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• Crémeux: French for "creamy". It is usually set with gelatin, chocolate or butter.

A plain stirred custard takes four ingredients.

• 2 cups of milk
• ¼ cup of sugar
• salt
• either 2 or 3 eggs

Mix it like this.

• Heat the milk to 75°C first to save time.
• Pull the chalazae, the white cords on the yolk, out of each egg with a fork.
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• Whisk the eggs only until yolk and white are blended, not until they foam.
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• Mix in the sugar and salt, and stir in the milk.

To cook it as a sauce:

• Use a double boiler. Put just enough water in the bottom pan that the top pan does not touch it, boil it, then turn it down to a simmer.
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• Chill an empty bowl in ice water so it is ready.
• Cook the custard in the top pan, stirring all the time with a rubber spatula and scraping the sides. Go slowly; it takes about 10 to 15 minutes.
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• It is ready when it leaves a coat on a clean metal spoon and is about as thick as a thin white sauce. Dip a spoon in the raw mix first, so you can see the change.
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• Pour it at once into the cold bowl, add vanilla, and keep stirring until it is cool.
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A good stirred custard has these qualities.

• smooth, never curdled
• about as thick as heavy whipping cream
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• mildly eggy
• lightly sweet
• colored by the yolks

A three-egg custard reaches its coating point at a lower temperature than a two-egg one, and it needs more attention while it cooks. Even made from one recipe, two stirred custards can turn out differently and thicken at different temperatures.

Baked custards

A baked custard has the same base as a stirred one: dairy, sugar and eggs, most often whole eggs. Whole eggs give a firmer, steadier custard. Yolks alone make it richer and softer. A baked custard can be a dessert on its own, a pie filling, or the base of another dessert. A good one holds a clean, sharp edge when you cut it.

• Heat the milk or cream and add it to the eggs slowly. Warm liquid shortens the baking time and helps the custard cook evenly.
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• Skim the foam off the top of the mix. Foam left on spoils the look of the baked custard.
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• Bake at a low heat, 325°F, since a cooler oven makes overcooking and curdling less likely. A plain custard is also baked at 375°F, and crème brûlée and flan at 350°F.
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• Set the cups in a water bath so the edges and center cook at the same pace. Each cup can sit on a wire rack in very hot water that comes nearly as high as the custard.
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• Test with a thin knife in the center. If it comes out clean, the custard is done. Or push a clean metal knife half an inch below the surface near the center and look for no custard sticking to it.
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A good baked custard has these qualities.

• pale golden brown
• smooth and evenly set, with no holes
• a uniform gel that holds a clear cut edge
• slightly sweet, with a mild egg taste

Some pies are baked custards too. Pumpkin and sweet potato pies set because of their eggs. They need no water bath, but a low oven still helps them cook evenly. Cheesecake is a dense baked custard, again set by eggs. It does go in a water bath so it cooks evenly and stays smooth. Overbaked, it cracks. When it is done, turn the oven off, open the door a little and let the cake cool inside.

Four classic custards

Crème brûlée.

• Heat half-and-half with sugar to about 80°C.
• Whisk egg yolks with vanilla, then pour the hot liquid in slowly while whisking.
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• Bake in a hot water bath at 350°F for 45 to 55 minutes, until a knife comes out clean.
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• Cool the cups quickly in an ice bath.
• Sprinkle sugar on top and brown it under the broiler.
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Flan.

• Spread caramel sauce in the bottom of each cup, which stands in for caramelizing sugar there.
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• Heat milk and sugar to about 80°C and whisk it slowly into an egg beaten with vanilla.
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• Bake and chill as for crème brûlée.
• Run a knife around the cold custard and turn it out onto a plate.

Chocolate pot de crème. This one is not baked. Heat cream, chocolate chips and sugar in a double boiler, stirring, until the chocolate melts and the mix reaches about 85°C. Whisk it slowly into pasteurized egg yolk and vanilla, then cool in an ice bath.

Eggnog. Whisk pasteurized egg yolk, milk and sugar, and stir it in a double boiler until it reaches 77°C. Cool it over ice, then add the cream and vanilla, cover and chill. Eggnog made from raw eggs has caused outbreaks of food poisoning, and pasteurized eggs are the safer choice wherever a recipe would use raw ones. see chapter 15: Pasteurized eggs in place of raw

Steamed puddings

Some puddings cook in steam, either in a commercial steamer or in a steamer set up on the stove. The best known is Christmas pudding, also called plum pudding: dense, rich and usually served in cold weather. see chapter 9: How to steam

Cooling, storing and holding custards

A custard is safest when it moves through the danger zone, 4°C to 60°C (40°F to 140°F), as fast as possible. Cooked food must drop from 60°C (140°F) to 20°C (68°F) within two hours. It then has four more hours to get from 20°C down to 4°C (40°F).

• Never cool a big pot of custard whole. Divide it into single servings first, then cool them.
• Stir it in a container set in ice water. Stainless steel or aluminum passes heat well; plastic does not.
• Shallow pans, no more than 5 cm (2 in.) deep, cool fastest. Do not stack them, and leave them loosely covered until cold, then cover tightly.

Store finished custards at 4°C (40°F) or colder. Keep dairy products between 2°C and 4°C (36–39°F), wrapped and in an area of their own, because milk fat soaks up strong smells.

A food held refrigerated longer than 24 hours needs a label with the day it was made and a "serve by" date. As a rule, throw out a PHF that has not been used within three days of being made.

A baked custard is cooled, then covered and refrigerated. That cooling must still meet the two-stage times above.

35.2 Dessert sauces

The common dessert sauces and how to plate them are in see chapter 22: Dessert sauces and see chapter 28: Sauces on the dessert plate.

Crème anglaise goes further than a sauce. Vanilla is its classic flavor, but coffee, spices, chocolate or a liqueur work too. Add more yolks and heavy cream and it becomes the base for French ice cream. Add more yolks with gelatin, whipped cream and a flavor and it becomes Bavarian cream. Keep it at or below 85°C (185°F) as it cooks, the same ceiling as other custards. see chapter 7: Eggs

Sabayon is yolks, sugar and a flavor whisked over simmering water until thick, then whisked until cool. It is often made with a sweet white wine or a spirit. Spooned over fresh fruit and browned under the grill, it is called a gratin. Italy's version, zabaglione, uses Madeira wine.

Fruit butter holds no butter. The name describes its thickness: whole fruit cooked down and reduced, puréed if you want it smooth. A fruit sauce is a purée cooked with starch and usually served cold. Hard sauce is butter, sugar and flavoring, often liqueur, piped and chilled, then set on a warm steamed pudding just before it goes out.

Safe handling for egg sauces

Crème anglaise, curd and sabayon are all cooked egg mixtures, which means 74°C (165°F), held for 15 seconds or more, and the two-stage cooling rule for any made ahead. A crème anglaise served warm from a hot-holding unit must stay at 60°C (140°F) or hotter. Put it in only once it is already at 74°C (165°F); a holding unit is not built to reheat cold food.

Sauce on the plate

A few rules guide the sauce on a dessert plate.

• A pool of sauce need not cover the plate. A smaller pool keeps the sauce from swamping the dessert, and some modern plates use very little sauce at all.
• Whatever the amount, choose for balance.
• Keep the sauce less sweet than the dessert, so the other flavors come through.
• Taste comes before looks.

35.3 Ice cream and frozen desserts

Still-frozen and churn-frozen

• Ice: water, sugar and fruit juice, with no dairy.
• Sherbet: fruit juice and sugar stirred into milk.
• Ice cream: cream and half-and-half sweetened and flavored.
• Frozen mousse: whipped cream with sugar and flavor, rich in fat and air, sometimes set with a little gelatin.
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Small crystals

The aim is small ice crystals. Their size depends on the interfering ingredients in the mix and on how it is made, so it varies between desserts: an ice is expected to have much larger crystals than a mousse. Whatever the kind, a frozen dessert should taste of what it is, feel smooth rather than grainy, and be firm yet easy to spoon. Why crystals grow, and what stops them, is in see chapter 7: Ice cream.

The United States standards

In the United States, the 2022 Code of Federal Regulations sets what a commercial frozen dairy dessert must contain before it can use the name. Some of these rules may not apply to products labeled "light" or "reduced calorie".

Both must contain nutritional sweeteners. Figures from the United States 2022 Code of Federal Regulations.

Using an ice cream freezer

The machine itself is described in see chapter 3: Ice cream machine. To use an electric freezer cooled by ice and salt:

• Wash and rinse the can, the dasher (the paddle inside) and the lid.
• Pour the cold mix into the can, fit the dasher, put the lid on, and set the can in the outer tub.
• Mix coarse rock salt with crushed ice at 1 part salt to 6 parts ice, by volume. Put about 3 inches of ice in the bottom of the tub, then add ice and salt in layers, packed a little higher than the mix inside the can.
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• Run the machine for 20 to 30 minutes.
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• Pack the dessert into pint containers, cover them, label them and put them in the freezer.

Ice cream, sherbet, ice and mousse

Vanilla ice cream. Stir ¾ cup of half-and-half with ½ cup of sugar and 1½ teaspoons of vanilla until the sugar has dissolved. Add 1½ cups of whipping cream and churn.

Orange milk sherbet.

• Rub grated orange zest into the sugar.
• Add lemon and orange juice, and stir until the sugar dissolves.
• Stir this slowly into very cold milk.
• Churn. If the milk curdles a little, the frozen sherbet's texture does not suffer.
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Cranberry ice.

• Boil water, sugar and a dash of salt until the sugar dissolves.
• Let it cool.
• Add cranberry juice cocktail and lemon juice.
• Still-freeze part of it in a loaf pan covered with foil, and churn the rest.
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Fruit or apricot mousse.

• Soften gelatin in cold water and dissolve it with heat, then stir it into the fruit.
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• Whip cold cream with a pinch of salt until it starts to thicken.
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• Add the sugar, and whip on to soft peaks; for the fruit mousse, stop before it is stiff.
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• Fold the cream into the fruit.
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• Pour into a pint container, cover, label and freeze.

Freezer safety and storage

Keep frozen desserts at −18°C (0°F) or colder. If the freezer warms above that, food can lose color and vitamins, and chilling it down again does not repair the damage.

Wrap everything well. Food left open in the freezer dries out on the surface and shows white or gray dry patches, called freezer burn, which spoil both texture and flavor. The cause is sublimation: ice on the surface turning to vapor and leaving tough, dry spots. Rotate stock first in, first out, which takes extra care in a chest freezer.

An ice cream base made with eggs, such as the French one in Dessert sauces above, is a cooked egg mixture. It follows the custard rules, 74°C (165°F) for 15 seconds and then two-stage cooling, and only a cooled mix goes into the freezer can.

35.4 Molecular techniques in the pastry shop

Molecular gastronomy brings new tools into the pastry kitchen.

• thickeners that work cold
• foams
• unusual gels
• powders
• liquid nitrogen
• small burst-in-the-mouth spheres

Many of the ingredients come from specialty food stores or online suppliers.

Thickening without heat

Some thickeners work with no cooking at all. Modified starch and xanthan gum are blended straight into a cold liquid, so a sauce keeps a fresh, raw taste. Xanthan, carrageenan and alginate as sauce thickeners are covered in see chapter 22: Gums and modern thickeners.

Foams and espuma

A foam is air trapped in a liquid or a solid. Mousse, soufflé, whipped cream and the froth on a cappuccino are all foams, and bread, pancakes and muffins are foams that have set. To build one, dissolve a thickener or gelling agent in a liquid or a purée, then whip it until it is as stiff as you want. Some mixtures break down if whipped too long without a stabilizer.

Espuma is Spanish for froth or foam, and in the kitchen it means a foam pushed out of a siphon (ISO) bottle charged with gas. A siphon needs no egg or other emulsifier, so the flavor stays pure, and it puts far more air into the mix than whipping does. Choose naturally light, thin flavors, since a strong one fades as air goes in. A stabilizer helps it hold its shape but is not always needed, and a filled siphon can be stored ready for service.

A well-made foam adds flavor without bulk, and it changes texture as it melts in the mouth. Gelatin and lecithin are common stabilizers for it.

Gels: firm, brittle and fluid

Setting a liquid such as a fruit purée lets you cut it into shapes. Gelatin works, and so does agar agar, made from red algae; both are described in see chapter 7: Gelatin, agar and pectin.

• A brittle gel is firm but fragile. Its network is weak, so it crumbles and melts in the mouth and releases its flavor as it breaks. Agar agar makes one, though with sugar it turns more elastic. Carrageenan, locust bean gum and low-acyl gellan gum give brittle gels as well. How much gelling agent and how much liquid you use both change the result.
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• A fluid gel sits between a sauce, a gel and a purée. It holds still like a solid but flows when stirred or shaken, and the harder and longer it is worked, the more fluid and finer it gets. It has a rich, creamy texture and can be served hot or cold, since many of its gelling agents survive high heat.
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Drying and powders

Drying a food concentrates its flavor and changes its texture; a dried apple crisp is nothing like a fresh slice. Grind it to powder and it changes again. Maltodextrin, or tapioca maltodextrin, mixed into a fat turns it into a powder. Maltodextrin dissolves in water, so a powdered olive oil or peanut butter becomes oil again on the tongue.

Liquid nitrogen

Liquid nitrogen freezes food with no freezer. It is clear and colorless at −196°C (−321°F), and it is used mostly to make ice cream and frozen foams. It is poured onto the food, freezes it, then boils off in a thick fog that can be part of the show. It is never eaten. Give it time to boil away completely and let the dish warm enough that it cannot hurt the diner.

Spherification

Spherification turns a liquid into small spheres with a thin skin and a liquid center that bursts in the mouth. They can be large or tiny, like "caviar", and soft or firm. There are two ways to do it.

• Direct. Dissolve sodium alginate in the flavored liquid, mixing well because it turns sticky, and let it stand until the bubbles are gone. Drip it from a spoon or syringe into a bath of water and calcium chloride or calcium lactate. A skin of gel forms on the outside only. Lift the spheres out and rinse off the calcium. Their skins are thin and break easily, so serve them at once.
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• Reverse. Drip a liquid that holds calcium into a bath of sodium alginate. A calcium alginate skin forms at once, but the setting stops at the skin and does not spread inward. The shells are thicker, so the spheres keep and need not be eaten straight away.
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Calcium lactate is often chosen over calcium chloride because it leaves no bitter taste.

The ingredients

Iota carrageenan is hydrated in cold liquid and then heated to about 70°C (158°F) while mixed hard; it sets anywhere from 40°C to 70°C (104–158°F), depending on how much calcium is present. Gellan gum starts to dissolve at 85°C to 95°C (185°F to 203°F). Kappa carrageenan gels melt back to liquid above 70°C (158°F).

Sous vide in the pastry shop

Sous vide, cooking food sealed in a bag in a water bath held at the food's target temperature, is covered in see chapter 10: How sous vide works. In the pastry shop it softens fruit and vegetables while keeping more of their vitamins and minerals than blanching or steaming does.