For the Cake

1. Preheat the oven to 350°F. Grease two 8-inch cake pans with Crisco and dust with flour to help easily release the cake after it is baked. I also line the bottom of the pans with parchment paper to ensure they don’t stick.
2. In a large mixing bowl, combine the sugar, vegetable oil, butter, eggs, egg yolks, and vanilla extract. Beat on medium speed until the eggs and oil are well incorporated and the batter is lighter in color, about 2 minutes.
3. Scrape down the bowl as needed. Next mix in the sour cream and beat until well combined.
4. In a separate bowl, combine the remaining dry ingredients. Alternate adding half the dry ingredients and half the buttermilk at a time and mix just until the flour starts to incorporate. Then add the remaining dry ingredients and buttermilk and beat until well combined. Use a spatula to scrape down the sides of the bowl and stir the batter from the bottom to the top to ensure it’s well mixed. Mix in the sprinkles by hand.
5. Divide the cake batter evenly between the two 8-inch pans. Bake at 350° F for 25 to 32 minutes. Check the cakes for doneness by inserting a toothpick into the center of the cake. If the toothpick comes out clean, the cake is done. Allow the cake to cool in the pans for 15 minutes. Then gently run a knife around the edges of the cake and flip them out of the pan and onto a rack to cool completely.

For the Frosting

1. In a microwave-safe bowl, break up the white chocolate into small pieces. Slowly melt in the microwave in 20-30 second increments, stirring each time until the chocolate is melted and smooth.
2. Divide the chocolate between 4 bowls, one ounce of melted chocolate per bowl. Use a toothpick to add the gel colors to the chocolate, just a touch is needed, stir until incorporated, but don’t overmix (this can cause the chocolate to seize).
3. Spread the chocolate in a thin layer on a piece of parchment paper and allow the chocolate to set firm, either on the counter or place in the refrigerator for 10-15 minutes until it’s firm. Once firm, remove the chocolate dice it into very small pieces, and set aside.
4. In a stand mixer using the paddle attachment, whip the butter for 3-5 minutes, scraping down the bowl occasionally. Beat until the butter is whipped to the same consistency as the cream cheese. Then add the cream cheese and combine it with the butter, beating until smooth.
5. Add 3 cups of powdered sugar with the vanilla extract, mix at low speed until the powdered sugar is incorporated, then increase the speed to high, beating for about 1 minute to ensure it’s well combined. Then add the remaining 2 cups of powdered sugar and salt, beat at low speed until incorporated then increase the speed until it’s light and fluffy. Reserve 1 cup of powdered sugar to add if the frosting seems too thin, add ½ cup at a time until the desired consistency is reached.
6. Once the frosting is whipped, add the chopped white chocolate, and incorporate it with a spatula, mixing to combine.

Assembly

1. Use a cake leveler to cut the domes off the top of the cake. Place a dollop of frosting on your cake board and place the bottom layer of cake on top of that.
2. Gently spread an even layer of frosting on top of the cake and place the next layer on top.
3. Proceed to frost the top and sides of the cake with a thin layer of frosting to create a crumb coat. Using an offset spatula or icing smoother, wipe away the excess frosting, leaving just enough to coat the outside of the cake. Do not mix your crumb-coating frosting back into your icing if it has cake debris in it. Then, frost the top and sides of the cake using your offset spatula. Once frosted, use a spoon or the spatula to create the swirls around the cake. Garnish with additional sprinkles if desired.