Preheat oven (electric cooker: 175 °C/circulating air: 150 °C/gas: see manufacturer). Line two baking trays with baking paper. Roughly chop the walnuts. Peel banana, crush with a fork.
Cream butter, sugar, 1 pinch of salt and vanilla sugar with the whisks of the mixer. Stir in the egg. Stir in banana puree and 2 pinches of cinnamon. Mix flour and baking powder and stir in.
Fold in the walnuts.
Using a tablespoon, place approx. 10 piles of dough on each tray at a slight distance and press slightly flat.
Bake cookies one after the other in a hot oven on the middle shelf for about 10 minutes until the edges are golden brown and the middle is still slightly soft.
Allow cookies to cool briefly on the tray, then pull them off the tray together with the paper and let them cool down on a cake rack.