Line a cookie sheet with baking paper. Scoop of the Nutella (about 1 1/2 tablespoons) and dollop on the lined cookie sheet. Place in the freezer.
Preheat the oven to 350F (180C).
In a small bowl, whisk together the butter, brown sugar and granulated sugar with a fork. Keep whisking until the butter is no longer separate/sitting on top of the sugar.
Whisk in the egg yolk and vanilla until evenly combined.
Add in the flour (be sure that the tablespoons aren't heaping!), baking powder and salt. Stir together until all the flour is incorporated.
Stir in 2 tablespoons chocolate chips (you'll use the rest for dotting on top of the cookie after its done baking).
Take about 3/4 of the dough and flatten slightly. Take the frozen (or firm) Nutella dollop and place in the middle of the dough. Place the remaining dough on top of the Nutella dollop. Pinch the edges of the dough around the Nutella so that its entirely covered in dough and roll into a ball.
Bake in the middle of the preheated oven for about 14-16 minutes or until the top looks set. Remove from the oven and carefully dot the top of the cookie with a few more chocolate chips