Preheat oven to 350°F. Line baking sheets with parchment paper or Silpat. Set aside.
In a large bowl, combine the cake mix, egg, and thawed whipped topping. (Note: The batter will be thick and sticky.)
Using a cookie scoop or tablespoon measure, form the dough into balls and roll in powdered sugar. Place 2 inches apart on the prepared pan.
Bake for 8-12 minutes or until the edges are golden brown.
Allow the baked cookies to cool on the pan for 3 minutes before transferring the cookies to a wire rack to cool completely.
Notes
Store the cooled cookies in an airtight container at room temperature for up to 3-4 days. For longer storage, you can freeze the cookies in a freezer-safe container for up to 2 months.