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

2. Add the bananas to a large bowl and mash with a fork. Divide the eggs, and add the egg yolks to the bowl with the banana and the egg whites to a separate bowl. Whisk with a pinch of salt until stiff peaks form. Set aside.

3. Add the oats, baking powder, vanilla extract and the chopped hazelnuts to the bowl with the bananas and egg yolks and mix until well combined. Gradually add the stiff egg white and fold in carefully – you want to keep as much volume as possible. Use a cookie scoop or spoons to place small amounts of dough on the baking sheet. Flatten a bit and bake for about 18-10 minutes. Take the cookies out of the oven and let them cool down a bit on the baking sheet, then transfer them to a wire rack and let cool down completely. Repeat with the remaining dough.