In a large bowl, use an electric mixer on medium speed to cream the butter and both sugars until light and fluffy, about 5 minutes. Beat in the eggs and vanilla extract.

Place 1/2 cup hazelnuts in a food processor and pulse into a fine powder. Roughly chop the remaining hazelnuts. In a medium bowl, combine the ground and chopped hazelnuts, flour, baking soda, salt and chocolate.

With the mixer on low, gradually mix the dry ingredients into the wet ingredients until just combined. Transfer the dough to an airtight container and chill in the fridge overnight.

Preheat the oven to 350 degrees F. Line a sheet pan with parchment. Roll the dough into 1/4-cup-sized balls and place on the prepared sheet pan about 2 inches apart. Press down the dough balls slightly with your hand. Bake for 18-20 minutes until golden brown, crisp at the edges, but soft in the middle. Cool on the sheet pan for 5 minutes before transferring to a wire rack.

Store in an airtight container.