Preheat oven to 350 degrees. Line two baking sheets with parchment paper.
Place hazelnuts on the baking sheet. Bake in preheated oven for 7 minutes.
Remove from oven and put warm hazelnuts into a dish towel. Rub the towel around to remove the skins.
Roughly chop the hazelnuts and set aside.
In a large bowl, combine gluten free flour blend, hazelnut flour, baking powder, baking soda, salt and milk powder. Whisk together until well combined. Set aside.
Add butter to the bowl of an electric mixer. Beat on medium speed about 2 minutes until smooth. Scrape down bowl.
Add the white and brown sugar to the butter. Beat 2-3 minutes on medium speed until light and fluffy. Scrape down the bowl.
Add the vanilla.
Add egg and yolk and beat about 60 seconds until combined.
Turn the mixer to the lowest setting. Slowly add the flour mixture stirring until just combined.
Remove bowl from stand. Add the chopped hazelnuts and the mini chocolate chips. Fold them in by hand until they are evenly incorporated.
Cover the bowl with plastic wrap and place in the refrigerator for 1 hour minimum.
After the chill, assemble the cookies as follows: 1. scoop a golf ball size amount of dough and place on cookie sheet leaving 2-3 inches between balls. 2. slightly flatten the dough ball, so it is a disc. Make an indentation in the center with your finger. 3. Add 1 teaspoon of hazelnut spread in the indentation. 4. scoop another gold ball size amount of dough. 5. flatten the second dough ball slightly in your hand and place over the top of the filled cookie.
Bake in preheated oven about 15 minutes. Cool on baking sheet for 5 minutes, then move to cooling rack to cool completely.