How to make
Beat the soft butter with the powdered sugar very well. Add the egg yolks one by one while constantly whipping, then the flour and the milk slowly.
Once the mixture is homogenized, add the cocoa, baking soda and vanilla. Mix at last with the beaten to snow egg whites and pour into a greased and floured form.
Bake the cake in a moderately preheated 360°F (180°C) oven until the toothpick comes out dry when you poke it. Let it cool and then serve it sliced.