Finely grind 25 g walnuts in the universal chopper. Knead 50 g butter, 3 tablespoons sugar, 100 g flour composition, 1 pinch of salt and ground walnuts first with the dough hooks of the hand mixer, then with floured hands to crumbles. Chill for about 30 minutes.
Cream 125 g butter, 125 g sugar, 1 pinch of salt and 1 packet of vanilla sugar with the whisk of the hand mixer. Stir in the eggs one by one. Mix 200 g flour composition with baking powder and cocoa, stir in alternately with the buttermilk
Coarsely chop 50 g walnuts. Peel banana, cut into slices and sprinkle with lemon juice. Fold walnuts and banana slices into the dough. Line the hollows of a muffin tray with paper baking cups, spread the dough into the cups. Sprinkle crumbles over the muffins, bake in a preheated oven (electric range: 175 °C/ convection oven: 150 °C/ gas: level 2) for 15-20 minutes
Take the muffins out of the oven and let them cool down for about 1 hour. Coarsely chop the chocolate coating, melt over a warm water bath, let it cool down for about 10 minutes. Pour the chocolate coating into a freezer bag, cut off a small corner, and spray thin lines over the muffins. Let dry in a cool place for about 30 minutes
waiting time approx. 1 1/2 hours