Chop 50 g chocolate coating. Peel 3 bananas, dice them finely and sprinkle with 2 tablespoons of lemon juice. Whip the fat, vanilla sugar, salt and sugar with the whisk of the hand mixer until creamy. Stir in the eggs one after the other. Stir in sour cream. Mix flour and baking powder and stir in briefly. Carefully fold in chopped chocolate and bananas.
Grease a box form (25 cm long) and sprinkle with breadcrumbs. Add the dough and smooth it down. Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for 50-70 minutes. Cover if necessary after approx. 45 minutes. Remove from the oven, let it rest on a cake rack for 10 minutes, then turn out of the tin. Let it cool down. Cut the cake in half horizontally. Chop 300 g chocolate coating, melt 75 g chocolate coating over a warm water bath, allow to cool slightly. Whip cream until stiff. Fold into two portions under the couverture. Spread the cream on the bottom cake and smooth it down. Place the upper cake on top. Chill for 1-2 hours.
Chop 300 g chocolate coating, melt 75 g chocolate coating over a warm water bath, allow to cool slightly. Whip cream until stiff. Fold into two portions under the couverture. Spread the cream on the bottom cake and smooth it down. Place the upper cake on top. Chill for 1-2 hours. Melt 225 g chopped couverture and oil over a warm water bath. Cover the cake with the chocolate coating, except for 2 tablespoons. Leave to dry. Peel and slice 1 banana, sprinkle with 1 tablespoon of lemon juice. Sprinkle cake with the remaining chocolate coating. Decorate with the banana slices. Leave to dry
Melt 225 g chopped couverture and oil over a warm water bath. Cover the cake with the chocolate coating, except for 2 tablespoons. Leave to dry. Peel and slice 1 banana, sprinkle with 1 tablespoon of lemon juice. Sprinkle cake with the remaining chocolate coating. Decorate with the banana slices. Leave to dry
3 1/2 hours waiting time