Tiramisu cake

Heat the oven to 350F. Lightly spray two 8-inch pans and line the bottoms with parchment rounds.

Separate five eggs. Put the whites in a medium bowl and reserve the yolks for the custard filling.

Add half a cup of whole milk and 120 g sour cream to the egg whites.

Add two teaspoons of vanilla and whisk the wet mixture together.

In the bowl of a stand mixer, combine 360 g cake flour with the sugar, baking powder and salt.

Substitution: to use all-purpose flour, measure 360 g, remove six tablespoons and replace them with six tablespoons of cornstarch.

Add 400 g granulated sugar to the dry ingredients, sprinkling it in rather than dumping it when weighing.

Add two teaspoons of baking powder and three quarters of a teaspoon of salt and whisk the dry ingredients together.

Fit the paddle attachment, start the mixer on low and add 226 g room-temperature unsalted butter a tablespoon at a time, mixing the fat into the flour before any wet goes in.

Run the mixer on low 30 seconds to a minute until the butter is worked in and the mixture is coarse crumbs with a wet, sandy texture and no large pieces.

On low, drizzle in half the wet mixture slowly, stop and scrape the bowl down, then add the rest to a thick batter.

Remove the paddle, scrape the bowl down and give the batter one final mix by hand.

Divide the batter equally between the two prepared 8-inch pans and level the tops with an offset spatula.

Optional: wrap damp cake strips around the pans to prevent doming.

Bake at 350F for about 35 minutes, until a skewer inserted in the centre comes out clean.

Cool the layers in the pan 15 minutes before inverting onto a wire rack; they are delicate and will crack if turned out too soon.

For the custard, put three quarters of a cup of whole milk in a small saucepan.

Heat the milk over medium for two to three minutes until steamy and just scalding.

Put the five reserved egg yolks in a medium bowl.

Whisk 100 g granulated sugar and one teaspoon of cornstarch into the yolks.

Take the milk off the heat once it bubbles and comes to a scald, then drizzle it slowly into the yolks while whisking vigorously so they do not scramble.

Pour the mixture back into the pot, set over medium low and whisk constantly until thickened; the frothy bubbles give way to slow thick burping bubbles. Whisk from the middle out to the edge and back.

Once thickened, drizzle in one tablespoon of coffee liqueur while whisking.

Transfer the custard to a bowl and cover the surface with parchment or plastic so it does not form a skin.

Set aside about 30 minutes, until roughly room temperature.

Whisk 16 oz room-temperature mascarpone until creamy; do not over whisk or it will curdle.

Fold half the cooled custard into the mascarpone gently until no streaks remain.

Fold in the remaining custard, then cover and refrigerate the filling.

If the filling looks grainy, gently mix in up to a quarter cup of heavy cream.

For the buttercream, heat about an inch of water in a medium pot. Put five egg whites in a heatproof bowl, with no yolk.

Add 300 g granulated sugar to the whites.

Add a pinch of salt and whisk together; the mixture will be sandy and grainy.

Set the bowl over the simmering water so the bowl does not touch the water.

Whisk gently and constantly for eight to 10 minutes, to 160F and smooth. Without a thermometer, test that it feels hot to the touch and rubs smooth between the fingers, elastic like a gel.

Transfer the egg mixture to a very clean stand mixer bowl fitted with the whisk attachment.

Whip on medium about 10 to 12 minutes, to glossy peaks that are no longer warm to the touch.

Bring two cups of unsalted butter to room temperature; if cold, microwave at half power in 10 second bursts.

On medium low, add the two cups of room-temperature butter one tablespoon at a time, letting each piece mix in completely before the next. The mixture will go soupy and will come back together.

After the last butter goes in, mix on medium high for two to three minutes. If still soupy, chill five minutes and remix, repeating until it stiffens.

If the buttercream is too cold and looks curdled, warm the top with a hairdryer briefly and mix again.

Add one teaspoon of vanilla and three tablespoons of coffee liqueur.

Scrape the bowl down, then mix on medium high about two minutes to glossy, sharp peaks.

The buttercream loses its texture on standing; re-whip 30 seconds before using it on anything visible.

For the syrup, measure three quarters of a cup of hot water; alternatively pull six shots of espresso and top up with hot water to three quarters of a cup.

Stir one and a half teaspoons of espresso powder into the hot water.

Stir in three tablespoons of coffee liqueur and set the syrup aside to cool slightly.

Slice each cooled cake into two even layers. Assemble with the cut side up so the layers absorb the syrup.

Re-whip the frosting, then load about a cup into a piping bag fitted with a medium round 1A tip. Load the chilled custard into a second piping bag.

Put the first layer down cut side up and brush or drizzle about a quarter cup of the coffee syrup over it for good coverage.

Spread a thin flat layer of buttercream over the soaked layer, then pipe a border round the edge to dam the custard.

Fill inside the border with a third of the custard, about a cup, and spread it level.

Dust about a tablespoon of cocoa powder over the custard.

Add the next layer cut side up and repeat: a quarter cup of coffee syrup, a thin layer of buttercream, a piped dam, a cup of custard, a dusting of cocoa powder.

If the cake feels wobbly or unstable, refrigerate it to set before continuing.

Add the third layer cut side up, aligning it, and repeat the syrup, buttercream, border, custard and cocoa.

Add the last cake layer cut side down.

Consolidate the frosting, whip it a final time, and reserve about three quarters of a cup for the dollops.

Coat the cake with the remaining frosting in a thin layer, pulling frosting from the top as needed; scrape back for a naked look or cover completely.

Smooth the sides with a bench scraper, smooth the top, then pull the top edge in for a clean edge.

The cake keeps about four days in the fridge and tastes better the day after it is made.

Dust the top with cocoa powder, then lift a little of it off with a spoon where the dollops will sit.

Pipe ruffled dollops of the reserved frosting round the top edge, touching each other for a clean line.

Set a chocolate covered espresso bean on every other dollop.

Chill at least an hour before serving.