1. Preheat oven to 350°.
2. In a large bowl, beat together the melted butter, brown sugar, granulated sugar, peanut butter, egg, and vanilla until smooth.
3. Add flour, baking powder, baking soda, and salt. Mix until well combined.
4. Stir in the chocolate chips.
5. Chill dough in the freezer for about 30 minutes.
6. Line baking sheets with parchment paper (or foil sprayed with cooking spray).
7. Roll dough into 1-inch balls. Flatten each ball slightly and place about 1/2 teaspoon of Nutella in the center.
8. Flatten another dough ball, place it on top, and pinch edges together. Roll gently into a ball to seal the Nutella inside.
9. Arrange on baking sheets about 2 inches apart.
10. Bake for 12–15 minutes, or until the edges get crispy and tops begin to crack. If the cookies don’t flatten after 5 minutes, gently press down with the back of a spoon.

Let cool on the baking sheet before serving.