In a large mixing bowl, use a mixer to beat together butter, cream cheese, vanilla extract, and egg until light and fluffy (2-3 minutes).

Gradually add yellow cake mix into the mixture, mixing on low until a smooth, sticky dough forms (1-2 minutes).

Cover the bowl and refrigerate dough for 30-60 minutes.

Scoop and roll dough into 1-inch balls, optionally rolling in sprinkles and then powdered sugar.

Bake in a preheated oven at 350°F for 10-12 minutes until edges are lightly browned.

Allow cookies to cool on the baking sheet for 5 minutes before transferring to a wire rack.