This recipe uses the whole-egg method and makes a moist and fluffy cocoa sponge cake. Have fun decorating it! I want to remember this recipe, so I'm writing it down here. This is the most delicious cocoa cake I have made so far.
Put the butter and milk into a heatproof bowl and microwave until the butter melts. Combine and sift the cake flour, katakuriko, and cocoa powder. Sift 2-3 times.
Put the eggs and sugar into a bowl and place the bowl over another bowl of hot water. Beat well until stiff peaks form. When warm to the touch, remove from the hot water bath and continue whipping.
When you can pierce the batter with a toothpick and it doesn't collapse, it's ready. Make sure you beat well until there are stiff peaks.
Add the sifted dry ingredients and fold in lightly, trying not to break the bubbles. Just until the flour disappears.
Add the melted butter from step 1 to the batter from step 4 and lightly fold it in. Pour the batter into a cake pan lined with parchment paper. Bake in an oven preheated to 170ºC for 25-30 minutes. It's done when a skewer inserted into the cake comes out clean.
When it's done baking, invert the cake and let it cool. You can leave it in the pan.
After it cools, remove the parchment paper and it's all done.
Have fun decorating your cake.
Story Behind this Recipe
Through a lot of trial and error, I came up with my own recipe for cocoa sponge cake. The scent and flavor of the cocoa made this cake come out just the way I wanted it.
The cocoa might clump, so make sure you sift very well. When you add the flour, mix in cutting motions to fold it in.