In a large bowl, cream together the butter and sugars until light and fluffy. Mix in the eggs one at a time until combined. Mix in the vanilla and peppermint extract.
In a separate bowl, mix together the flour, cocoa powder, baking powder and salt.
Slowly mix the dry ingredients into the wet ingredients until fully incorporated.
Cover and place in the fridge for at least 4 hours.
Preheat the oven to 350℉. Line baking sheets with parchment paper and set aside.
Add the powdered sugar to a shallow bowl.
Using a medium cookie scoop, scoop the dough into your hands and roll between your hands to smooth. Roll the cookie dough balls in the powdered sugar and place on the prepared baking sheet.
Bake in the preheated oven for 10-12 minutes. Allow to cool on the baking sheets for 3 minutes before transferring to wire racks to cool completely.