Preheat your oven to 350 degrees F. This is an essential step to ensure your cookies bake evenly. While the oven heats, line a large baking pan with parchment paper to prevent sticking.
In a large bowl, whisk together the flour, cocoa powder, baking soda, and salt. Mixing these dry ingredients first helps ensure that the baking soda is evenly distributed throughout the batter.
In the bowl of an electric mixer, cream together the butter and sugars until the mixture is light and fluffy, about 1 to 2 minutes. This process incorporates air into the dough, making for a soft and tender cookie.
Add in the egg, vanilla extract, and peppermint extract to the creamy butter mixture. Beat until everything is well combined and smooth, which should take about 30 seconds.
Gradually add the dry ingredients to the wet mixture, mixing on medium-low speed until just combined. Be careful not to overmix, as this can lead to tough cookies.
Cover the dough and chill it in the refrigerator for 30 minutes. Chilling the cookie dough is essential for achieving the right texture. It helps prevent the cookies from spreading too much while baking, resulting in a thicker, chewier cookie.
After the dough has chilled, use a cookie scoop to grab about 2 tablespoons of dough. Roll it into balls and place them on the prepared cookie sheet, leaving at least 2 inches between each ball to allow for spreading.
Bake the cookies in the preheated oven for 10 to 12 minutes. Look for edges that are set and may begin to crack. This ensures a perfect texture that’s crisp on the outside and chewy on the inside.
Once baked, remove the cookies from the oven and let them cool on the baking sheet for 5 to 10 minutes before transferring them to a wire rack. This step allows them to set and harden at the edges.
After the cookies have cooled completely, it’s time to frost them. In the bowl of an electric mixer, add the softened butter and powdered sugar and beat on high for about 1 minute. The frosting should be fluffy and creamy.
Add the remaining peppermint extract and 1 tablespoon of milk to the frosting. Beat slowly at first, then increase to medium-high speed until creamy. If you want a creamier frosting, add another teaspoon of milk and mix again.
To make colored frosting, divide the frosting into two separate bowls. Add a few drops of green food coloring to one bowl and red to the other. Whisk until the colors are well incorporated.
Frost the cookies and sprinkle with your choice of toppings: crushed candy canes, chopped Andes mints, or festive sprinkles!
Enjoy your homemade Mint Chocolate Cookies!