Add the cake mix, Cool Whip, and egg to a large bowl, and stir until a sticky dough forms.
Refrigerate the dough for 30 minutes.
Gather a cookie scoop of dough, and drop into the powdered sugar, roll it around to coat, then place on the baking sheet 2 inches apart. Flatten each dough ball slightly.
Bake for 8-10 minutes, until set.
Transfer the baking sheet to a cooling rack, and allow to cool for 5 minutes.
Carefully remove the cookies using a spatula, and transfer directly to the cooling rack.
Notes
Cake mix cookie dough tends to be sticky and soft due to the high moisture content in all cake mixes.
If you find the batter too sticky, try adding a small amount of all-purpose flour to the mix.