1. Preheat oven to 350° F. Place mini portion pan on a sheet pan. Lightly oil wells.
2. In a large bowl, whisk cake mix with eggs, milk, oil, and vanilla until just combined. Fold in sprinkles. Divide batter evenly between petites. Don’t overfill; batter will rise.
3. Bake 20–22 min, or until a toothpick comes out clean. Let cool completely before unmolding and icing, if desired.