In a large bowl combine cake mix, whipped topping and egg; mix until well combined. Chill the dough several hours or overnight (or freeze dough wrapped in plastic).
Preheat oven to 350 degrees F (175 degrees C).
Form tablespoons of dough into one inch balls and roll them in the confectioners' sugar. Place the cookies on greased or parchment lined cookie sheet a couple inches apart.
Bake 10 to 12 minutes until cookies are set, but not browned. Cool on wire rack.
