In a medium size bowl whisk together flour, cocoa, baking soda, and salt in a medium bowl. Set aside.
In a large bowl cream together the butter and sugar with an electric mixer. Add eggs and vanilla and mix until well combined. Next slowly add flour mixture to the wet ingredients and mix until combined. Stir in M&M’s and chocolate chips and then chill dough for about 20 minutes.
Once dough is chilled, pre-heat oven to 350°. Line baking sheet with parchment paper or Silpat.
Roll dough into balls and place on cookie sheets. Press a few chocolate chips and M&M’s into the tops of the dough just before baking.
Bake for about 10-12 minutes or until the edges are crisp and the center is still soft. Allow to cool on pan for 2 minutes and then transfer to a cooling rack.