Yellow cake with chocolate buttercream frosting

Grease two tall 8-inch cake pans and line them with custom parchment rounds: fold the paper twice, fold a triangle down twice in the same direction, snip to the length of the pan's radius and unfold.

Soften the butter, or speed soften it in the microwave on the lowest power in five second bursts, rotating the sticks. Stop when it is just barely pinchable; do not melt it.

Whip the butter by itself until as fluffy as possible before the sugar goes in.

Cream in 300 g granulated sugar as best you can until slightly lighter in colour, which shows the air bubbles that make the cake fluffy.

Beat in the first two eggs one at a time, then the two extra yolks.

Add the buttermilk and the vanilla. Warming the buttermilk and eggs to room temperature first gives an even fluffier texture but is not necessary.

Add the cake flour, baking soda, baking powder and salt and whip smooth, wiping down the sides of the bowl as needed.

The batter should be the consistency of jello pudding. Mix in a little more flour if it looks too loose.

Divide the batter evenly between the pans, checking by jabbing a handle into the centre of each, and bake at 350 F or 180 C, convection if you have it.

Tap the pan: if the centre jiggles it needs more time. When the jiggling stops, pierce it and look for a clean skewer. In his oven with tall narrow pans they took half an hour.

For the frosting, soften and whip 230 g butter until fluffy.

Beat in about 300 g powdered sugar. It will look like cheese curds at first; keep going and it turns to frosting.

Beat in 50 to 100 g cocoa powder.

Beat in the corn syrup for a dense gooey texture, then a heaped tablespoon of meringue powder so the buttercream holds its shape instead of dripping.

Loosen with a little water, milk or buttermilk so it spreads without tearing the cake, taste and adjust, and add a splash of vanilla. Judge the chocolatiness by taste, not colour, since it darkens as it dries.

De-pan the cakes onto a cooling rack by turning them into your hand, peel the paper off, and cool them completely - the rack can go in the fridge - or they will melt the buttercream.

Top the cooled layers with a serrated bread knife, shaving the humps off, and dust off the crumbs.

Dump almost half the frosting on the first layer and work it across and over the sides with an icing spatula, clearing the top for the second layer, then put the rest on top.

Let it fall over the edges and frost the sides, then lay the spatula almost parallel to the top and swish back and forth for waves. Go around the sides once more.

Wipe the plate edge with a wet towel. Chilling the cake gives the frosting a chewier, fudgier consistency thanks to the corn syrup.