01 - Preheat oven to 350°F. Line two baking sheets with parchment paper for easy cleanup.
02 - In a large bowl, beat softened butter and granulated sugar together until light and fluffy, about 2-3 minutes.
03 - Beat in the egg, vanilla extract, and peppermint extract until fully incorporated into the mixture.
04 - In a separate bowl, whisk together flour, cocoa powder, baking soda, and salt until well blended.
05 - Gradually add dry ingredients to the wet mixture, mixing on low speed until just combined. Avoid overmixing.
06 - Fold in semi-sweet chocolate chips until evenly distributed throughout the cookie dough.
07 - Drop rounded tablespoons of dough onto prepared baking sheets, leaving 2 inches between each cookie.
08 - Bake for 9-11 minutes until edges are set but centers remain slightly soft. Let cool on baking sheet for 5 minutes.
09 - While cookies cool, beat the softened butter in a medium bowl until creamy and smooth.
10 - Gradually add powdered sugar, mixing well. Add milk, peppermint extract, and green food coloring. Beat until fluffy.
11 - Once cookies are completely cool, spread or pipe green frosting generously onto each cookie.