In a bowl or stand mixer, cream together the softened butter and sugar until light and fluffy. Add egg and stir to incorporate.
Add hazelnut flour, type 00 flour, and pinch of salt to the butter mixture and stir with a spatula until the dough comes together. Cover and refrigerate for 1 hour.
Divide dough into 4 equal pieces. Roll each section into a rope, around 10 inches long. Using a sharp knife, cut each dough rope into 10 equal pieces.
Shape the dough sections into small balls, about 1 teaspoon each, and place them on a baking sheet. Place back into the fridge for 30 minutes.
Preheat your oven to 350°F.
Bake for 12-14 minutes, or until the bottoms just start start to turn brown.
Transfer to a cooling rack and let cookies cool completely.
While the cookies cool, melt chocolate chips in the microwave in 30 second increments, stirring in between.
Pair up the cookies based on size and shape.
Spoon a small amount of chocolate filling onto the flat side of one cookie and gently press another cookie on top to create a sandwich, forming the characteristic "kiss" shape.
Repeat until all cookies are paired and filled.
Allow to chocolate to firm up slightly and enjoy.