Ingredients:

  • 190g cake flour
  • 200g granulated sugar
  • 1.5 tsp baking powder
  • 0.5 tsp salt
  • 115g unsalted butter, room temperature
  • 3 large egg whites, room temperature
  • 60g full-fat sour cream
  • 120ml whole milk
  • 2 tsp vanilla bean paste
  • 60g rainbow jimmies sprinkles

Instructions:

  1. Preheat and Prep. Set your oven to 350°F (175°C) and line a 12 cup muffin tin with your favorite paper liners. Note: Preheating for at least 20 minutes ensures the oven temp is stable.
  2. Cream the Base. In a stand mixer, beat 115g of room temperature butter and 200g granulated sugar for 3 to 5 minutes until pale, voluminous, and fluffy.
  3. Whisk the Liquids. In a separate bowl, combine the egg whites, 60g sour cream, 120ml whole milk, and 2 tsp vanilla bean paste. Note: Whisk until no streaks of egg white remain.
  4. Slow Emulsion. Gradually pour the liquid mixture into the butter while the mixer runs on low speed. It may look slightly curdled, but keep going until it smooths out.
  5. Sift the Dry. Sift together the 190g cake flour, 1.5 tsp baking powder, and 0.5 tsp salt directly into the bowl.
  6. The Gentle Fold. Use a rubber spatula to gently fold the dry ingredients into the wet batter until just combined and no flour streaks are visible.
  7. Add the Confetti. Carefully fold in the 60g of rainbow jimmies. Do not over mix, or the colors will bleed into the batter.
  8. Bake to Perfection. Divide the batter evenly and bake for 18 minutes until a toothpick comes out clean and the tops spring back.
  9. Whip the Frosting. Beat 230g butter until smooth, then gradually add 480g powdered sugar, 45ml heavy cream, and a pinch of salt. Whip until it looks like a thick, white cloud.
  10. Cool and Pipe. Let the cupcakes cool completely on a rack before piping with the frosting. Wait until they are cold to the touch.