Cake

1. Preheat your oven to 375⁰F (190⁰C).
2. Grease and line two 20 cm cake pans so nothing sticks.
3. In a bowl, beat the 4 egg yolks with 170 g white sugar until thick and pale. 
4. In a separate bowl, mix 60 ml cocoa with 60 ml warm water until smooth.
5. Stir in the 75 g melted butter and 2 ml vanilla essence.
6. Add the cocoa mixture to the egg yolk mixture and beat until everything’s well combined. 
7. Sift together the 160 g Self-Raising flour and 10 ml baking powder, then gently fold into the batter. Don’t overmix or the cake can turn dense.
8. In a clean bowl, whisk the 4 egg whites until foamy, then add the 30 g white sugar and beat until soft peaks form. Not stiff, just softly holding shape.
9. Fold the egg whites into the batter in batches. Go gently, as you want to keep that air in.
10. Divide the batter between the 2 pans and bake for about 35 minutes, or until a skewer comes out clean.
11. Let the cakes sit for a few minutes, then turn out onto a rack to cool completely before icing. Warm cake plus icing equals a mess.

Icing

1. Beat the 150 g butter until creamy.
2. Add the 280 g icing sugar and a few drops of vanilla essence, and beat until smooth.
3. Slowly mix in the 12.5 ml warm milk and 45 ml sifted cocoa until you’ve got a spreadable, creamy icing. If it feels too thick, add a tiny splash more milk.
4. Spread a layer of icing between the cooled cakes, then cover the top and sides with the rest.