Line a small plate or tray with parchment and drop 10 teaspoon-sized scoops of Nutella on it. Freeze for 30 minutes, or until firm.
10 tsp nutella
In a medium bowl, beat the softened butter, brown sugar, and granulated sugar until creamy. Mix in the egg yolk and vanilla.
4 tbsp butter, 1/4 cup brown sugar, 2 tbsp granulated sugar, 1 egg yolk, 1 tsp vanilla extract
Add flour, cornstarch, baking soda, and salt. Stir until just combined, then fold in chocolate chips. Do not overmix!
1/2 cup flour, 1 & 1/2 tbsp corn starch, 1/4 tsp baking soda, 1/4 tsp salt, 1/2 cup semi sweet chocolate chips
Scoop dough into 10 balls (about 2 tbsp each). Flatten a dough ball, place a frozen Nutella scoop in the center, and wrap the dough around it to seal completely. Roll smooth.
Repeat, removing Nutella from the freezer one piece at a time so it stays solid.
Freeze the stuffed dough balls for 30 minutes. white you preheat the oven to 350°F. Chilling is what makes them thick and gooey instead of thin and flat.
Bake for 12–14 minutes or until edges are lightly golden and centers look slightly underbaked.
Cool on the baking sheet for 15 minutes, they finish setting as they cool.