They are kind of thick and have small bombs of dark chocolate and lots of crunchy hazelnuts. They are really good! And chocolate and hazelnuts are just always a really good match.
Preheat the oven to 200 degrees Celsius (392 degrees Fahrenheit).
Whisk butter, sugar, and brown sugar together well – until it becomes light and fluffy.
Whisk in the egg.
Add all the remaining ingredients to the bowl and whisk at low speed until you get a firm and coherent dough.
Place small balls of dough (about the size of walnuts) on a baking sheet with parchment paper. They spread out, so make sure there is enough distance between them.
Bake for about 8 minutes, take them out and let them cool on a baking rack. They only become completely crispy once they have cooled.
Serve with an ice-cold glass of milk or a good cup of tea/coffee.