Preheat oven to 350 °F (175 °C) and line two baking sheets with parchment paper.
In a large bowl, combine the cake mix, thawed Cool Whip, and egg. Stir with a spatula until the mixture forms a thick, sticky dough with no dry streaks.
Place powdered sugar in a shallow bowl.
Scoop dough by rounded tablespoons and roll each portion into a ball.
Roll each dough ball generously in powdered sugar until fully coated.
Place coated dough balls on the prepared baking sheets, spacing them about 2 inches apart.
Bake for 10–12 minutes until the edges are set but the centers still appear slightly underdone.
Allow cookies to cool on the baking sheet for 5 minutes, then transfer to a wire rack to cool completely.
