Add the flour, cocoa, baking soda, and salt in a large bowl. Stir together and set aside.
In the base of a stand mixer with a paddle attachment (or bowl with a hand mixer), beat the butter, sugar, and brown sugar together on medium high. Cream the butter and sugars together until light and fluffy (2-3 minutes).
Add the egg, peppermint, and vanilla to the butter mixture on medium-high speed.
On low speed, add the dry ingredients in three parts until combined. When just combined, mix in the chocolate chips.
Cover and place in the fridge to chill for at least 2 hours.
Remove cookie dough from the refrigerator for 15 minutes. Preheat the oven to 350°F and line a baking sheet with parchment paper.
Scoop the dough and roll into balls (1.5 tablespoons each). Roll each ball lightly in granulated sugar and then roll again in powdered sugar (generous coating). Place 3 inches apart on the baking sheets.
Bake the cookies for 11 minutes. If the cookies aren’t spreading, a few minutes before they are done baking, remove them from the oven and lightly bang the baking sheet on the counter to help them spread.
Cool cookies and enjoy! These cookies are delicious frozen!