01 -
Preheat oven to 350°F (175°C). Spray a 6-inch mini cake pan (with 2-inch high sides) with cooking spray. Line the bottom with parchment paper by tracing the pan on parchment, cutting it out, and fitting it in.
02 -
Beat together the softened butter and granulated sugar with an electric mixer until light and fluffy, approximately 1-2 minutes.
03 -
Incorporate the vanilla extract and egg white, beating until well combined.
04 -
Add the flour, baking powder, and salt. Beat briefly to combine, then add all of the milk. Mix until smooth, being careful not to overmix the batter.
05 -
Gently fold in the sprinkles until evenly distributed throughout the batter.
06 -
Pour the batter into the prepared pan and place on a baking sheet. Bake for 30 minutes, or until a toothpick inserted in the center comes out with only moist crumbs.
07 -
Allow the cake to cool slightly before gently turning it out onto a plate. Remove the parchment paper from the top of the cake.
08 -
Beat together the softened butter, powdered sugar, and milk until smooth and fluffy. Fold in the sprinkles last.
09 -
Frost the cooled cake, slice, and serve.