Add the butter and semi-sweet chocolate chips to a medium saucepan and melt over medium heat, stirring frequently.
Remove from heat and allow to rest until cool for 10 – 15 minutes.
In a mixing bowl, whisk together the flour, cocoa powder, baking powder, baking soda, and salt and set aside.
In the bowl of a mixer, whip together the light-brown sugar, granulated sugar, eggs, and vanilla on medium-high speed until pale and fluffy, about 1 minute.
Using a rubber spatula stir in the melted chocolate mixture. Working in 3 separate batches, add 1/3 of the flour mixture and fold just until combined.
Chill dough for about 45 minutes. Preheating the oven to 325 degrees during the last 10 minutes of chilling.
Scoop a tablespoon of the dough out and shape it into balls.
Place onto Silpat or parchment paper lined baking sheets, spacing them 2 inches apart.
Bake in preheated oven 12 – 13 minutes, then remove from oven and allow to cool on baking sheet 5 minutes before transferring to a wire rack to cool completely.