In a large bowl, whisk together the flour, cocoa powder, baking powder, and salt.
Using a mixer (hand or stand), cream together both sugars and butter for a minute. Add and incorporate one egg at a time then add in the peppermint.
Turn speed to low and add in flour mixture slowly until a sticky dough is formed.
Chill dough in freezer for 10 minutes.
Sift powdered sugar into a bowl and add a heaping teaspoon sized ball of dough, rolling lightly to coat in sugar so you are able to roll it in your hands to make in a ball. Roll again in powdered sugar to coat more.
Line a baking sheet with parchment paper and place 12 coated dough balls on each tray.
Cook, one sheet at a time for 11 minutes.
Cool for 5 minutes then transfer to a wire tray.
Okay, so that's exactly how it's written.
My changes. I sift the flour and cocoa powder. Otherwise lumps can be visible. I also don't put it in the freezer, I put it in the fridge for a few hours or even overnight. The firmer the dough the easier it is to roll. I roll the dough in my hands then roll it in the powdered sugar. I didn't find the two rolls necessary. I also cook for around 13 minutes, maybe my cookies are larger? Maybe I just like a firmer center.