Preheat your oven to 350°F (175°C) and line a baking sheet with parchment paper.
In a large mixing bowl, whisk together the melted butter, brown sugar, and granulated sugar until well combined.
Add the eggs one at a time, mixing well after each addition, followed by the vanilla extract.
In another bowl, sift together the flour, cocoa powder, baking powder, and salt. Gradually mix the dry ingredients into the wet mixture until just combined.
Fold in the semi-sweet chocolate chips, white chocolate chips, and dark chocolate chunks until evenly distributed.
Using a cookie scoop or tablespoon, drop balls of dough onto the prepared baking sheet, leaving about 2 inches of space between each cookie.
Bake in the preheated oven for 10-12 minutes, or until the edges are set but the centers are still soft.
Remove from the oven and allow to cool on the baking sheet for 5 minutes before transferring to a wire rack to cool completely.
Notes
Allow cookies to cool completely for best texture.