Into a big mixing bowl, add the room temperature butter, and the Nutella, and cream it with an electric hand mixer for 2-3 minutes or until it’s creamy and light in color.
Step 2: Add the brown sugar, salt, vanilla extract, and sugar and mix until well combined for about 1-2 minutes.
Add the eggs, and egg yolk, and mix until combined and creamy. Add the flour, chopped hazelnuts, and baking soda, and mix with the hand mixer until almost combined.
Step 4: Add the chocolate chips, and fold with a spatula until the mixture is just combined. Cover the bowl with plastic wrap and let the dough rest in the fridge for at least an hour. We let the dough rest in the fridge overnight.
Use a cookies scooper to scoop out the cookies or scoop the cookies with a regular tablespoon, 1 ½ tablespoon at a time. Dip the cookie dough balls in chopped hazelnuts until they are coated with hazelnuts.
Step 6: Place the cookie dough balls onto a parchment paper-lined baking sheet, and bake in a 180c (350f) preheated oven for 11-12 minutes.
Melt some Nutella spread and top the cookies with small dollops of the Nutella. Let the cookies cool for 5 minutes, and then transfer them to a wire rack to cool completely.