In a medium saucepan, melt the butter over medium-low heat. Once melted, bring it to a gentle boil. Stir or swirl the pan until the milk solids begin to brown and the butter turns an amber color. Remove from heat and let it cool.
Line a large baking sheet with parchment or wax paper. Using a teaspoon, drop 24 scoops of Nutella onto the prepared baking sheet. Place the baking sheet in the freezer for at least 20 minutes while you prepare the cookie dough.
In a large bowl, combine the cooled butter, brown sugar, and granulated sugar using a rubber spatula or wooden spoon until well mixed. Add the egg, egg yolk, vanilla extract, baking powder, baking soda, and salt. Mix until smooth.
Gradually stir in the flour, followed by the chocolate chips. Chill the dough in the refrigerator for 15 minutes.
Preheat your oven to 375°F (190°C). Line another baking sheet with parchment paper.
Using a 3-tablespoon cookie scoop, scoop out the chilled cookie dough. Press a well into the dough, place a frozen scoop of Nutella inside, and encase it with the dough to form a ball.
Place the cookie dough balls on the prepared baking sheet, spacing them about 3 inches apart. Return any unused Nutella to the freezer to keep it frozen.
Bake the cookies for 8 minutes, or until the edges are golden. Remove from the oven and let them cool on the baking sheet for 3-4 minutes before transferring to a wire rack to cool completely.
Notes
For a fun twist, try adding chopped nuts or a sprinkle of sea salt on top before baking. Make sure to keep the Nutella frozen until you're ready to use it for the best gooey center!