Preheat oven to 350F.
Line two baking sheets with parchment paper.
In a small bowl combine flour, cocoa powder, baking soda and salt. Set aside.
In a standing mixer, beat together the butter and sugars until combined and fluffy.
Beat in the egg, and vanilla extract.
Gradually beat in the dry ingredients until combined.
Fold in 1½ cups of the M&Ms.
Using a medium ice cream scooper, scoop out some dough onto the parchment paper.
Sprinkle remaining M&Ms on top.
Bake in the oven for 10-12 minutes.
Remove from oven and cool completely.