For the banana cake, beat the eggs, sugar, cocoa and water until foamy. Alternately stir in the flour mixed with baking powder and the oil.
Line a baking tray with baking paper and spread the mixture evenly on it. Bake in the oven at 180 °C for about 35-40 minutes.
Cook the vanilla pudding according to package instructions and let cool. Cream the butter with the powdered sugar and add the pudding by the spoonful, finally add the lemon juice.
Spread the cooled cake with the jam and top with the finger-thick banana slices. Spread the lemon cream on top and cover with a thin layer of chocolate icing.
Chill the banana cake for a while and cut into slices to serve.