Peel 3 bananas, cut into small cubes. Knead 50 g sugar, butter and 100 g flour into crumbles.
Beat 2 eggs, 75 g sugar, 1 packet vanilla sugar and oil with the whisks of the hand mixer until creamy. Mix 175 g flour, baking powder, salt and cinnamon. Stir the flour mixture and milk into the egg mixture.
Fold in banana cubes. Fill into a greased, flour-sprinkled box form (6.5 x 11 x 30 cm) and smooth it down. Spread crumbles on top and bake in a preheated oven (electric cooker: 175 °C/ circulating air: 150 °C/ gas: see
manufacturer) bake for about 45 minutes. Remove and let cool on a cake rack.
Carefully remove the cake from the tin and cut it in half horizontally. Melt the chocolate over a warm water bath. Separate 2 eggs. Mix the egg yolks with 1 packet of vanilla sugar until creamy. Beat the egg whites until stiff, while pouring in 1 tablespoon of sugar.
Whip the cream until stiff. Decorate the surface of the cake with chocolate using a spoon. Stir the rest of the chocolate into the egg yolk cream. Alternately stir in cream and beaten egg white bit by bit.
Peel and slice 1 banana. Place the lower part of the cake on a plate and enclose it with a cake frame or a frame made of aluminium foil. Spread half of the chocolate mousse on top.
Spread banana slices on top, finish with the remaining mousse. Place the upper cake half on top and chill for about 2 hours.