Step 1

Place the chopped bittersweet chocolate in a microwave-proof glass bowl and heat at 20 second increments, stirring between each interval, until the chocolate is just melted. Set aside and allow the chocolate to cool for 5 to 10 minutes or until lukewarm.

Step 2

In a medium bowl, whisk together the flour, cocoa powder, baking soda, and salt. Set aside. Using stand mixer fitted with a paddle attachment, beat the butter at medium speed for a minute until creamy. Add the brown sugar and granulated sugar and beat until light and fluffy, about 2 to 3 minutes. Add the egg, peppermint, and vanilla extract and beat until well combined. Beat in the melted (lukewarm) chocolate. On low speed, slowly add the flour mixture until just absorbed. Using a rubber spatula, scrape the bottom of the bowl to ensure that all of the ingredients are well incorporated.

Step 3

Gently stir in the M&M holiday mints. Scoop the dough into 1-inch balls and set on a plate. Cover with plastic wrap and allow the dough to chill in the fridge for 45 minutes to 1 hour, or until firm.

Step 4

Preheat the oven to 350°F (176°C) with a rack in the center position. Transfer the chilled cookie dough balls onto a parchment-lined half sheet pan, setting them apart by about 2 to 3 inches. I recomend only baking 8 cookies on one sheet pan.

Step 5

Bake for 10 to 14 minutes, rotating the pan halfway, or until the cookies have set on the outer edges, but are still somewhat soft in the center. Remove and allow the cookies to cool completely on a cooling rack.