01 - Preheat the oven to 350°F (175°C). Line two baking sheets with parchment paper.
02 - In a large bowl, beat the butter, granulated sugar, and brown sugar until light and fluffy.
03 - Add eggs, vanilla extract, and peppermint extract; beat until combined.
04 - In a separate bowl, whisk together flour, cocoa powder, baking soda, and salt.
05 - Gradually add dry ingredients to the wet mixture, mixing just until incorporated.
06 - Fold in chocolate chips.
07 - Scoop tablespoon-sized balls of dough onto the prepared baking sheets, spacing 2 inches apart.
08 - Bake for 9-11 minutes, until edges are set but centers are still soft.
09 - Let cookies cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.
10 - In a medium bowl, beat butter until creamy. Gradually add powdered sugar, milk, and peppermint extract, beating until smooth and fluffy. Add green food coloring and mix to achieve desired color.
11 - Once cookies are completely cool, spread or pipe green mint frosting on top of each cookie.