To make the chocolate cakes, in a saucepan, melt the butter with the chopped chocolate. Cream the sugar, vanilla sugar and with the eggs.
Mix the flour with the baking powder, salt and cocoa and gently add alternately to the butter and chocolate mixture. Finally, add the white chocolate.
Pour the mixture into a greased cake pan and bake the chocolate cake in a preheated oven at 180 degrees for about 40 minutes.