Turn oven on to 350 degrees to pre-heat. In the mixing bowl of a stand mixer, add the Butter, Brown Sugar, and Sugar, and mix for about 1 minute, or until creamy and fluffy. Add the Egg, and Vanilla, and mix until combined.
In a separate bowl mix together the Flour, Cocoa, Baking Soda, and salt. Gradually add the flour mixture to the mixing bowl, and blend on low just until mixed. Remove the mixing bowl, and scrape the sides of the bowl, and blend until smooth. The cookie dough will be thick.
Line a cookie sheet with a silicone baking liner. Scoop out a scoop of cookie dough, with a cookie scoop, and place the scoop on the Silicone lined cookie sheet. Press M & M's and chocolate chips all around the scoop of cookie dough, until it's covered.
Bake for 10 to 12 minutes, or until cookies begin to turn golden brown around the edges.
Remove the cookies to a wire rack to cool completely. Serve, and Enjoy!