In a large bowl whisk together the flour, cocoa, baking soda and salt. Set aside.
In a separate large bowl, beat together the butter and sugar until fluffy.
Then beat the Nutella into the butter mixture.
Beat the egg and vanilla into the butter and Nutella mixture.
Add the dry ingredients into the butter mixture. Do a few stirs by hand first, then beat in the dry ingredients until evenly combined.
Turn off the mixer and scrape down the sides of the bowl using a large wooden spoon or rubber spatula. Stir in the chocolate chips. I always stir in 3/4 cup and reserve the 1/4 cup for dotting the top of each cookie.
Cover the bowl with plastic and refrigerate for 30 minutes or up to 48 hours.
When ready to bake, preheat the oven to 350F (180C) degrees. Line 2 cookie sheets with parchment paper or silicone baking mats.
Form the cookies into balls with about 1.5 to 2 tablespoons of dough each (I recommend using a cookie scoop), and place the cookies 2 inches apart on the lined cookie sheets. If the dough is too hard to form into balls, let it sit on the counter for 10 minutes first.
Bake 1 tray at a time in the middle rack of the preheated oven for 9-11 minutes, or until the tops look set.
Remove from the oven and allow the cookies to cool fully on the cookie tray. Optionally, dot the tops of each warm cookie with a few extra chocolate chips.