01 - Preheat the oven to 350°F (175°C). Line two baking sheets with parchment paper.
02 - In a large mixing bowl, cream together butter, granulated sugar, and brown sugar until light and fluffy.
03 - Beat in 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 chocolate chips.
07 - Drop tablespoon-sized balls of dough onto the prepared baking sheets, spacing them 2 inches apart.
08 - Bake for 10–12 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 - For the frosting, beat the softened butter until creamy.
11 - Gradually add powdered sugar, milk, peppermint extract, green food coloring, and salt, beating until smooth and fluffy. Add more milk if needed for a spreadable consistency.
12 - Once cookies are completely cool, frost each cookie with a generous layer of green mint frosting.