01 - Preheat oven to 350°F. Line two baking sheets with parchment paper.
02 - In a large bowl, cream together the butter, granulated sugar, and brown sugar until light and fluffy.
03 - Beat in the eggs one at a time, then add vanilla and peppermint extracts.
04 - In a separate bowl, whisk together flour, cocoa powder, baking soda, and salt.
05 - Gradually add the dry ingredients to the wet mixture, mixing until just combined.
06 - Fold in the chocolate chips.
07 - Drop tablespoon-sized balls of dough onto the prepared baking sheets, spacing them about 2 inches apart.
08 - Bake for 9 to 11 minutes, until edges are set. Cool on the baking sheets for 5 minutes, then transfer to a wire rack to cool completely.
09 - Beat the butter until creamy. Gradually add powdered sugar, then milk and peppermint extract. Mix until smooth and fluffy.
10 - Add green food coloring until desired shade is reached.
11 - Once cookies are cool, spread or pipe frosting on top of each cookie.
12 - Allow frosting to set before serving.