How to make
Beat the butter with the sugar. Add the egg yolks one at a time while mixing. Add the milk, then the flour, which you've mixed with baking powder beforehand.
Throw in the vanilla and mix well. Beat the egg whites to snow and add them to the rest of the mixture. Separate 5 tablespoons of the mixture and mix it with the cocoa.
Smear the cake pan with grease and flour and pour a layer of the yellow dough in. On it, spread some of the cocoa paste unevenly. Top with the remaining yellow mixture and put it to bake in a moderate oven.
Leave the finished cake to cool for 15 minutes. Finally, top with the white chocolate couverture.