1. Preheat the oven to 350°F (180°C). Line a baking sheet with baking parchment and set aside.

2. Add the bananas to a large bowl and mash with a fork until only small chunks remain. Add the sugar and hazelnut butter and mix until well combined.

3. If you use rolled oats add them to a mixer/food processor and mix until you get a fine flour – some larger pieces are ok. Add the baking powder, cinnamon, and salt and mix to combine. Add the dry ingredients to the bowl with the banana mixture and fold in. Next, add the chopped walnuts and fold in as well.

4. Use a large cookie scoop and place dough portions with some space in between on the prepared baking sheet. Flatten the dough portions slightly – the cookies are not spreading a lot. Sprinkle with some additional chopped nuts (optional) and bake for 16-17 minutes. The edges should have browned slightly. Take out and let cool down on a wire rack. If you were not able to bake all cookies at once, repeat with the remaining dough.