Ingredients:
1/2 cup (115g) unsalted butter, softened to room temperature
1/2 cup (100g) granulated sugar
1/2 cup (100g) packed light or dark brown sugar
1 large egg, at room temperature
1 teaspoon pure vanilla extract
1 teaspoon coffee extract
1 cup (125g) all-purpose flour
1/2 cup + 2 Tablespoons (53g) unsweetened cocoa powder
1 teaspoon baking soda
2 teaspoons espresso powder or 1 Tablespoon instant coffee granules
1/8 teaspoon salt
1 bag (8 oz) Cafe Mocha M&Ms (or substitute any other chocolate candy)

Directions:
In a large bowl using a hand-held mixer or stand mixer fitted with a paddle attachment, beat the butter for 1 minute on medium speed until completely smooth and creamy. Add the granulated sugar and brown sugar and beat on medium high speed until fluffy and light in color. Beat in egg, vanilla and coffee extracts on high speed. Scrape down the sides and bottom of the bowl as needed.

In a separate bowl, whisk the flour, cocoa powder, baking soda, espresso powder, and salt together until combined. On low speed, slowly mix into the wet ingredients until combined. Add in the M&Ms and mix on low speed.

The cookie dough will be sticky. Cover dough tightly with aluminum foil or plastic wrap and chill for at least 3 hours (or 30 minutes in the freezer!) and up to 3 days. Chilling is mandatory for this cookie dough.

Preheat oven to 350°F (177°C). Line two large baking sheets with parchment paper or silicone baking mats. (Always recommended for cookies.) Set aside. Remove dough from refrigerator and let sit at room temperature if the dough can't be easily scooped.

Scoop and roll balls of dough, about 1.5 Tablespoons of dough each, into balls and place on the baking sheets. Bake the cookies for 8-9 minutes. The cookies should have a crackled appearance with a soft center. Allow to cool for 5 minutes on the cookie sheet. They will slightly deflate as you let them cool. Transfer to cooling rack to cool completely.

Recipe adapted from: http://sallysbakingaddiction.com/2015/12/07/peppermint-mocha-cookies/