1. Roughly chop the semi-sweet chocolate and milk chocolate, as well as the walnuts. Divide the walnuts – half of them are for the dough, the rest is for the decoration. Set everything aside.

2. Add the butter and both of the sugars to a large bowl and mix on high for a few minutes until very light and fluffy. Add the egg and vanilla extract and mix in. In a separate bowl, mix the flour with baking powder and salt. Add everything to the large bowl and mix until just combined. Next, add the chopped chocolate and half of the chopped walnuts and fold in. Place the dough in the fridge for at least 2 hours (or overnight).

3. Preheat the oven to 350°F (180°C). Line a baking sheet with baking parchment. Prepare a small bowl with the remaining chopped walnuts for the decoration. Use a cookie scoop* or a tablespoon to scoop dough out of the bowl and then press it into the walnuts. Place the dough portions on the baking sheet with some space in between – the cookies will spread slightly.

4. Bake the cookies for about 12 minutes – the edges of the cookies should be firm and slightly browned. The centers of the cookies should be still a bit soft. Remove the cookies from the oven and let cool down a bit on the baking sheet, then transfer to a wire rack and let cool down completely. Repeat with the remaining dough and bake more cookies.