Line 2 baking sheets with parchment paper or silicone baking mats. Set aside.
In the bowl of an electric mixer, combine the butter and sugars. Beat together on medium speed until light and fluffy, about 2 minutes. Blend in the egg, vanilla, and peppermint extracts. Scrape down the bowl if needed.
In a separate bowl, whisk together the flour, cocoa powder, baking soda, and salt. Slowly add the dry ingredients into the wet ingredients in the mixer on low speed just until incorporated. Fold in the chocolate chips.
Either chill all the dough in the fridge for at least an hour then roll into balls or you can roll dough into balls first then chill. Roll 1.5 tablespoons of dough into balls.
When ready to bake, preheat the oven to 350˚ F.
Place the cookie dough balls on the baking sheets. The cookies don’t spread much so if you like them less thick, press down slightly.
Bake 8-9 minutes. Let cool on the baking sheets for about 5 minutes, then transfer to a wire rack to cool completely.