Preheat oven (electric cooker: 180 °C/circulating air: 160 °C/gas: see manufacturer). Grease a box mould (25 cm long; approx. 1.7 l capacity) and dust with flour. Melt 100 g butter and peanut cream. Mix 200 g flour, baking soda, 1 pinch of salt and cocoa. Chop dark chocolate. Peel the bananas and finely mush them with a fork. Mix with butter mix, eggs and 100 g sugar. First stir in the flour mixture, then the chopped chocolate.
Fill the dough into the mould and smooth it down. Bake in a hot oven for 50-60 minutes. Take out, let rest in the form for about 10 minutes, then turn out. Let it cool down on a cake rack.
Melt 1 tablespoon of brown sugar in a frying pan. Stir in nuts, caramelise slightly. Pour onto baking paper and allow to cool. Chop milk chocolate, melt in a hot water bath and spread on the cake with a spoon. Sprinkle with nuts.