Line a baking sheet or cutting board that can fit into your freezer with parchment paper. Using a small cookie scoop, spoon small scoops of Nutella and drop onto the parchment. The rounder the shape, the easier it will be to form into cookies. Place tray into freezer.
Meanwhile, make the cookie dough.
Combine flour, cocoa powder, baking soda, baking powder, and salt in large bowl and set aside.
In the bowl of a stand mixer, cream together butter and the 2 1/4 cups sugar with the paddle attachment until light and fluffy. Start on low speed to combine and then crank it up to high speed. Scrape sides.
Reduce speed to low and add the eggs and vanilla. Mix until combined.
Slowly add the dry ingredients and mix on low just until combined. Fold in the crushed hazelnuts.
Cover and chill for at least one hour in refrigerator to firm up the dough.
When ready to bake, preheat oven to 350 degrees F. Line a large baking sheet with parchment paper or a silpat. Add a small amount of sugar to a small bowl for rolling. Remove Nutella balls from the freezer.
Using a large cookie scoop, scoop cookie dough and transfer it to your hand and flatten it to a disk. Place a frozen Nutella ball in the center and wrap the dough around, sealing all the edges and then rolling to make a nice smooth round ball. Set on the prepared baking sheet. Set cookies about 3 inches apart. Keep remaining Nutella balls in the freezer while not using.
Bake in preheated oven 14-16 minutes. The top of the cookies will begin to crinkle. Allow cookies to rest on the baking sheet about 5 minutes once removing from oven and then immediately transfer to a cooling rack.
Cookies can be stored in an air tight container at room temperature for several days or frozen and thawed later.