Dollop the Nutella in rounds that are about 1 teaspoon big on parchment lined baking pans. Freeze.
Preheat the oven to 350°F. Line two baking sheets with parchment paper and set aside.
In a medium bowl, mix together the flour, baking soda, baking powder, and salt. Set aside.
In a mixer, beat the sugar and butter together until light and fluffy. Beat in the egg, yolk, and vanilla until fully incorporated. Mix in the flour until just mixed.
Get a tablespoon of dough and create an indentation. Stick in a frozen dollop of Nutella. Add another half tablespoon of dough.
Roll the dough into a nice ball, then roll in sugar to coat. Place on a baking sheet. Repeat with all the dough and Nutella.
Bake for 8 - 10 minutes, or until the cookies just start to get light touches of brown on the edges.
Allow the cookies to sit on the baking sheets for a minute before transferring to a wire rack to cool completely.