1. Add the butter, brown sugar, and hazelnut butter to a large bowl and mix for 2-3 minutes until very light and fluffy. Add the egg and vanilla extract and mix until well combined. Mix the flour, cornstarch, baking powder, and salt – add to the bowl and mix until just combined. Add the chopped chocolate and crushed cookies and fold in. Place the bowl with the dough in the fridge for at least 30 minutes.

2. Preheat the oven to 375°F (190°C). Line a baking sheet with baking parchment and set aside. Take the dough out of the fridge and divide it into 8 portions. Shape each portion into a ball. Pull those balls apart, so you get two halves with a rough surface, then press those two halves together with the rough surfaces facing up – this will give the cookies a rougher look. You don’t want the dough portions not be too tall/high, because they do not spread a lot.

3. Bake the cookies for about 12 minutes. Take out of the oven and let cool down for a while on the baking sheet, then transfer to a wire rack and let cool down completely.

4. If you like, you can decorate the cookies with some additional caramel sauce and/or melted chocolate before serving (optional).