PRE-HEAT oven to 350°F.
MIX cake mix, whipped topping, butter and egg on medium until blended.
FOLD in 1/2 c. M&M's®.
DROP batter by teaspoonfuls into powdered sugar to coat. Place on un-greased baking sheets.
PRESS a few M&M's® on top of each dough ball.
BAKE 10 to 12 minutes or until edges are lightly browned and tops are crackled.
Remove to wire rack immediately. Cool completely before serving. (In fact these are one cookie that taste better the longer they sit.)