Separate 1 egg. For the crumbles, mix 125 g flour, cocoa and 75 g sugar. Melt butter and add to the mixture. Add the egg yolks, knead into crumbles and place in the fridge. Roughly chop the mint tablets. Peel bananas and cut into fine slices. Beat 2 eggs and egg whites, 100 g sugar, vanillin sugar and oil.
Mix baking powder, 250 g flour, salt and cinnamon. Stir the flour mixture and buttermilk briefly into the egg mixture. Fold in banana slices and chopped bars. Fill into a greased, sugar-spread box form (25 cm long). (Silicone mould not suitable; see No.: F32211) Spread crumbles evenly on top. Bake in a preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for approx. 1 hour. Remove from the oven and leave to rest in the mould for approx. 15 minutes. Turn out of the mould, let cool completely and serve dusted with cocoa