Preheat oven to 375°F.

In a shallow bowl, mix together powdered sugar and cornstarch with a fork or small whisk. Set aside.

In a mixing bowl, combine butter, cake mix, and eggs by hand using a sturdy spoon. When combined, roll into balls about 1-inch in diameter. Roll balls in powdered sugar mixture and transfer to a baking sheet, about 12 per sheet.

Bake for 10-11 minutes or until set. Cool for 1-2 minutes on baking sheet before moving to a cooking rack. Store in airtight container.