In a bowl mix together the cake mix, cool whip and egg. It will form a thick cookie batter. Cover the bowl with plastic wrap and refrigerate for 45 minutes to firm it up.
Preheat oven to 350F. Line cookie sheet with parchment paper. Add powdered sugar in a bowl.
Use small cookie scoop to scoop out dough, use hands to roll into a ball. Roll into powdered sugar and then on to sheet pan. Make sure there is room for cookies to expand on sheet.
Bake for 9-11 minutes or until the top has crinkled and is no longer raw dough in the center, the outside edges should be firmed up.
For chewy cookies this typically takes 9 minutes, leave on the sheet until cooled. For crispy cookies bake for 11 minutes and leave on baking sheet.