Ingredients:

  • 1 box (15.25 oz / 432 g) yellow or vanilla cake mix
  • 1 box (3.4 oz / 96 g) instant vanilla pudding mix
  • 3 large eggs
  • 1/2 cup (115 g) unsalted butter, melted
  • 1 cup (240 ml) whole milk
  • 1/2 cup (120 g) sour cream
  • 1 tsp (5 ml) vanilla extract
  • 1 cup (225 g) unsalted butter, softened
  • 4 cups (480 g) powdered sugar
  • 2 tbsp (30 ml) heavy cream
  • 1 tsp (5 ml) vanilla extract
  • 1 pinch salt
  • 1/2 cup (60 g) rainbow nonpareils

Instructions:

  1. Preheat your oven to 325°F (163°C). Line a 9x13 inch baking pan with parchment paper, leaving an overhang on the sides.
  2. In a large bowl, whisk together the cake mix and pudding mix until combined.
  3. Add the eggs, melted butter, milk, sour cream, and vanilla extract. Whisk until the batter is smooth and free of lumps, avoiding overmixing.
  4. Pour the batter into the prepared pan, smoothing the top with a spatula.
  5. Bake for 30-35 minutes, or until a toothpick inserted in the center comes out clean and the edges are just starting to pull away from the sides.
  6. Allow the cake to cool completely in the pan, then refrigerate for 30 minutes before cutting.
  7. Lift the cake out of the pan using the parchment handles and use a 2-inch circular cookie cutter to carve out 12 uniform circles.
  8. Whip together softened butter, powdered sugar, heavy cream, vanilla extract, and salt until fluffy.
  9. Transfer frosting to a piping bag. Pipe a generous dollop on each cake dot and smooth it flat with a spatula.
  10. Immediately press the sides and top of the frosting into the rainbow nonpareils to create a seamless coat.