Preheat oven to 350°F (175°C) and line two baking sheets with parchment paper.

In a mixing bowl, cream together the softened butter, granulated sugar, and brown sugar until fluffy.

Beat in the egg and peppermint extract until well combined.

In a separate bowl, whisk together flour, cocoa powder, baking soda, and salt. Gradually add to wet ingredients until just combined.

Fold in chocolate chips.

Scoop tablespoon-sized balls of dough onto prepared sheets and space evenly.

Bake for about 10 minutes until edges are firm but centers are soft. Allow to cool slightly before enjoying.