In a mixing bowl, whisk together the flour, cocoa powder, baking soda and salt
In a separate mixing bowl, mix butter until creamy
Mix in both sugars to the butter until creamy
Mix in the egg, vanilla extract, milk into the sugar butter mixture
Combine the flour mixture and the butter mixture and add food coloring
Mix until dough is formed and fold in the M&Ms
Cover the dough with plastic wrap and let chill in the refrigerator for at least 1 hour and up to 2 days
Preheat oven to 350° and line baking sheet with parchment paper
Form dough into golf ball-sized balls and place on parchment paper an inch apart
Bake for 11-12 minutes
Let cool for 5 minutes, and enjoy