Beat the melted butter with the sugar until frothy. Then add the beaten eggs. Peel the bananas and mash them well with a fork. Add to the rest of the flour with the flour and stir. Stir in baking powder and milk. Chop the couverture. Finally add the vanilla sugar together with the chopped couverture and cocoa and mix.
Bake in a greased loaf pan for about 40-45 minutes.