Grind 25 g walnuts in the universal chopper. Knead ground walnuts, 50 g butter, 25 g sugar, 75 g flour and 1 pinch of salt to form crumbles. Chill for about 30 minutes.
Cream 125 g butter, 125 g sugar, 1 pinch of salt and vanilla pulp. Stir in eggs. Mix 200 g flour, baking powder and cocoa, stir in with buttermilk
Coarsely chop 50 g walnuts. Peel and slice the bananas and sprinkle with lemon juice. Fold nuts and bananas into the dough. Line the hollows of a muffin tray (12 hollows) with 1-2 paper baking cups each. Spread the dough in them. Sprinkle crumbles over it. Bake in the preheated oven (electric cooker: 175 °C/ convection oven: 150 °C/ gas: level 2) for approx. 25 minutes. Let them cool down
Roughly chop the chocolate, melt it and put it into a freezer bag. Cut off a small corner and spray thin chocolate lines over the muffins. Let dry for about 30 minutes
waiting time approx. 1 1/2 hours