Step 1: Preheat your oven to 350°F (175°C). Line your baking sheets with parchment paper to prevent the cookies from sticking.
Step 2: In a medium bowl, whisk together the all-purpose flour, cocoa powder, baking powder, baking soda, and salt. Set this mixture aside.
Step 3: In a large mixing bowl, combine the softened butter, granulated sugar, and light-brown sugar. Cream these together on medium speed until light and fluffy.
Step 4: Add the eggs, one at a time, mixing well after each. Stir in the vanilla extract until fully incorporated.
Step 5: Gradually add the dry ingredient mixture to the wet mixture, mixing on low speed until just combined. Be careful not to overmix!
Step 6: Gently fold in the semi-sweet and milk chocolate chips using a spatula or wooden spoon.
Step 7: Scoop out small spoonfuls of Nutella and place them on a plate lined with parchment paper. Freeze for about 15-20 minutes until firm.
Step 8: Take a portion of the cookie dough, flatten it, place a frozen Nutella dollop in the center, and wrap the dough around it, ensuring it's enclosed.
Step 9: Place the stuffed cookie dough balls on the prepared baking sheets, spacing about 2 inches apart. Sprinkle sea salt on top if desired. Bake for 10-12 minutes.
Step 10: Allow the cookies to cool on the baking sheet for about 5 minutes before transferring to a wire rack. Enjoy warm!