Prepare the Dough : In a large bowl, whisk melted butter, granulated sugar, and brown sugar until combined. Add eggs one at a time, whisking well after each addition. Stir in vanilla extract. In a separate bowl, whisk together flour, cocoa powder, baking powder, and salt. Gradually fold the dry ingredients into the wet mixture until fully combined. Gently fold in the semi-sweet and milk chocolate chunks.

Chill the Dough : Cover the dough and chill in the refrigerator for 30 minutes. This helps prevent spreading during baking.

Bake the Cookies: : Preheat oven to 350°F (175°C) and line baking sheets with parchment paper. Using a cookie scoop or spoon, place dough balls (about 2 tbsp each) onto the prepared sheets, spacing 2 inches apart. Bake for 12–14 minutes until the edges are set but the centers remain soft. Allow cookies to cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.