Start by lining a small cookie sheet with parchment paper.
Scoop out 17 portions of Nutella onto the baking sheet and freeze them until firm.
Preheat your oven to 350 degrees F and line two baking sheets with parchment paper.
Roughly chop the Ferrero Rocher and set them aside.
In a medium bowl, whisk together the flour, cocoa powder, baking powder, and salt.
In a large bowl, cream together the softened butter and sugars until fluffy.
Add the egg yolks and vanilla to the butter mixture and mix until pale and fluffy.
Gradually add the dry ingredients to the wet ingredients and mix until combined.
Fold in the chopped Ferrero Rocher with a rubber spatula.
Using a large cookie scoop, portion out the dough into balls. Flatten each ball and place a frozen Nutella ball in the center. Enclose the Nutella with the cookie dough and roll into a ball again.
Transfer the cookie dough to the prepared baking sheets and bake for 10-11 minutes.
Once out of the oven, use a round cookie cutter to shape the cookies for a perfect circular shape.
Let the cookies cool for 10 minutes, then transfer them to a wire rack to cool completely. Sprinkle chopped hazelnuts and sea salt on top before serving.
Get ready to treat yourself to the ultimate Nutella experience with these heavenly cookies!