Beat the butter with 250 g sugar and 1 packet of vanilla sugar until frothy. Stir in the eggs one at a time. Mix in the flour, cocoa and baking powder alternately with the milk. Spread the dough evenly on a greased drip pan in the oven that has been sprinkled with breadcrumbs. Bake at 175 °, fan oven 150 °, gas mark 2 for 30-35 minutes. Let cool and then turn out onto a large platter.
Drizzle the cake with the coffee and let it steep for about 1 hour.
In the meantime, stir the mascarpone with quark, 2 sachets of vanilla sugar and 50 pieces of sugar until creamy.
Spread the cream on the floor. Cover the surface with chocolate bars. Chop the couverture and melt it with 1 teaspoon butter in a water bath and stir well. Put in a freezer bag, cut off a small corner. Decorate the cake with mocha beans and couverture and dust with a little cocoa.