For the chocolate casserole, heat the milk in a saucepan and melt the chocolate in it – then let it cool.
Mix butter, sugar, vanilla sugar and cocoa powder. Add chocolate milk and fold in flour and baking powder. Pour this mixture into a greased baking dish.
Melt the chocolate, milk and margarine and empty into the chocolate mixture. The chocolate sauce should sink to the bottom.
Bake the casserole in the preheated oven at 180 °C for about 40 minutes.