Prep: Preheat your oven to 375 degrees F. Then, line a baking sheet with parchment paper or spray with a non-stick cooking spray. Set aside.
Cream butter: In a medium size mixing bowl, using a handheld electric mixer cream together the butter and brown sugar until fluffy.
Then, add in the egg and peppermint extract, beat again until combined.
Add dry ingredients: In a separate small bowl, stir together the flour, cocoa powder, baking soda, and salt. Mash out any lumps that have formed by using your fingers or a spoon.
Next, add the dry ingredients to the wet mixture and combine well but be sure to not overmix.
Then, stir in the chocolate chips, scraping the bottom of the bowl as you go to make sure that everything is evenly blended.
Bake: Proceed to place spoonful's of cookie dough onto the prepared cookie sheets, at least a few inches apart so that there is room for the cookies to expand.
Bake in the oven for 8-10 minutes.
Remove from oven and transfer the cookies to a wire cooling rack to cool completely. Serve slightly warm and enjoy!