Step 1

Make the cake: Preheat the oven to 350°F (180°C). Lightly spray three 8-inch cake pans with nonstick spray. Line the bottoms with parchment paper rounds and spray again.

Step 2

In a large bowl, whisk together the sour cream, eggs, and egg whites until evenly combined. Add the vanilla and milk and whisk until incorporated.

Step 3

In the bowl of a stand mixer fitted with a paddle attachment, combine the granulated sugar and salt. Sift in the cake flour, baking soda, and baking powder. Mix on low speed to incorporate.

Step 4

Cut the butter into tablespoon-sized pieces. With the mixer running on low speed, add the butter to the dry ingredients, one piece at a time. Continue mixing until a sandy, coarse meal forms, 3–4 minutes.

Step 5

With the mixer running on low speed, pour in one-quarter of the wet ingredients at a time and mix to incorporate, scraping down the sides of the bowl between each addition. Continue mixing until the batter is smooth.

Step 6

Remove the bowl from the stand mixer and gently fold in the sprinkles with a rubber spatula.

Step 7

Divide the batter evenly between the prepared cake pans, tapping the pans on the counter a couple of times to release any large air bubbles.

Step 8

Bake the cakes for 25–30 minutes, until a toothpick inserted into the center of a cake comes out clean. Set the pans on a wire rack and let the cakes cool completely, about 1 hour. Once cooled, run an offset spatula around the edges of the pans to loosen the cakes, then invert onto the rack and remove the parchment rounds.

Step 9

Meanwhile, make the frosting: In a large bowl with an electric hand mixer (or in a stand mixer fitted with the whisk attachment), whip the butter on medium speed until creamy, about 3 minutes.

Step 10

With the mixer running on low speed, add the powdered sugar, about 1 cup at a time. Once incorporated, add the cream, vanilla, and salt. Increase the mixer speed to high and beat for 3 minutes, until the frosting is fluffy.

Step 11

Assemble the cake: Using a large serrated knife, slice a thin layer off the top of each cake to create a flat surface. Discard the scraps.

Step 12

Smear a bit of frosting onto an 8-inch cake round set on top of a cake stand, then place a cake layer on the round. Use a large offset spatula to spread an even layer of frosting over the cake. Place another cake layer on top and frost. Place the last cake layer, bottom-side up, on top and spread a thin layer of frosting over the top and sides of the cake to make the crumb coat. Refrigerate for 15 minutes, until the frosting is set.

Step 13

Generously spread a thick, even layer of frosting over the top and sides of the cake. Decorate the cake with the remaining frosting and sprinkles as desired.

Step 14

Slice and serve. Cake can be kept at room temperature for 2 hrs and refrigerated for 3 days.

Step 15

Enjoy!