In a stand mixer, cream together the butter, granulated sugar, and brown sugar on medium speed for 5 minutes.  Mixture is done when it is light and fluffy.  You will need to stop the mixer a few times to scrape the sides of the bowl with a spatula.

Beat in the eggs and vanilla on medium speed for 2-3 minutes, until thoroughly combined.

Using a food processor, grind ½ cup of the hazelnuts to a fine powder.  Chop the rest of the hazelnuts.  In a medium bowl, combine the ground and chopped hazelnuts, flour, baking soda, salt, and chocolate.

On low speed, slowly add the flour mixture into the butter-sugar mixture, and continue to mix until the flour mixture is completely incorporated and the dough is evenly mixed.

Chill the dough for 3 hours or overnight in an airtight container in the fridge.  When ready to bake, preheat oven to 350 degrees and place oven rack in the center of oven.

Using a cookie scooper (approximately 1.5 tablespoon size), scoop out dough balls and place on parchment paper lined baking sheet.  Gently flatten the top of the dough with palm of your hand.

Bake for 16-18 minutes, until the tops of cookies are browned.  Leave cookies in a little longer, if you'd like a deeper brown and more of a crunch.  Let the cookies cool on the baking sheet on a wire rack for 5 minutes, then transfer cookies to the wire rack for further cooling.  Enjoy!!