Yellow cake with chocolate buttercream

Set the oven to 350F, lightly grease three 8-inch cake tins and add parchment paper rounds to the bottoms.

Whisk 400 g all-purpose flour, 42 g cornstarch, 1 tablespoon baking powder and three quarters of a teaspoon salt together in a medium bowl and set aside.

In a mixer fitted with a paddle, beat 170 g room temperature unsalted butter with 400 g sugar on medium for three minutes, until light and fluffy and lightened in colour.

Add a third of a cup of neutral oil and 1 tablespoon vanilla.

On medium, add four eggs one at a time, each cracked into a separate bowl first, then scrape the bowl down.

Add three egg yolks; the batter should stay fluffy and glossy without breaking.

On the lowest setting add the flour mixture in three additions alternating with the 1.5 cups buttermilk in two, working quickly so the batter is not overmixed.

Scrape down and finish folding by hand until evenly mixed with no unmixed flour. Measuring the flour correctly, using room temperature ingredients and not overmixing are the three things that make a cake perfect.

Variation: a 9 by 13 inch sheet cake bakes 30 to 35 minutes; cupcakes filled two thirds bake 20 minutes and make 32; three 9-inch pans bake 20 to 25 minutes.

Divide the batter between the pans, weighing to check, and smooth flat with an offset spatula.

Soak the cake strips, wring them mostly out and fasten them around the pans for a flat, evenly baked layer.

Variation: the layers can be made ahead, wrapped well and frozen for about three months, then thawed and decorated.

Bake at 350F for 25 to 30 minutes; the centre should spring back when lightly touched, or a skewer should come out clean.

For the frosting, melt a quarter cup of unsalted butter and mix in a quarter cup, 25 g, of cocoa powder to bloom it, then set aside.

Combine 90 g semi-sweet chocolate chips with a quarter cup of whole milk in a heat-safe bowl and microwave in 30 second bursts, stirring between, until melted and smooth; residual heat finishes the last lumps as it cools.

Beat the remaining 1.75 cups room temperature unsalted butter with the paddle on medium for about a minute until creamed.

Add the cocoa mixture and mix, scraping the bowl down so no unmixed butter is left.

Add five to six cups of sugar slowly on low, tasting as you go; he stopped at five cups.

Add half a teaspoon of salt; it can go in with the creamed butter, the ganache or the bloomed cocoa instead.

Add the ganache once it is room temperature, not warm, and mix on low; scrape down again.

If it is stiff rather than luscious, add milk or cream a tablespoon at a time; then mix on medium-low until swoopy, without pumping in so much air that it turns frothy.

Spread one cup of frosting on each layer with an offset spatula, stack the three layers and put the remaining frosting on top.

Work the frosting slowly over the sides for full coverage before swooping, so the delicate crumbs are not disturbed, then swoop with the spatula.

Chill at least 30 minutes so it sets, then slice; it keeps covered in the fridge up to five days. The frosting darkens as it dries.