For the Cupcakes

1. Preheat the oven to 350°F. Line a cupcake pan with cupcake liners.
2. In a large mixing bowl, combine the sugar, vegetable oil, butter, eggs and 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. Scrape down the bowl as needed. Next mix in the sour cream and beat until well combined.
3. In a separate bowl, combine the remaining dry ingredients and sift together. Alternate adding half the dry ingredients and half the buttermilk at a time mixing at a low speed 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.
4. Using a large cookie scoop, divide the batter evenly, filling each liner 2/3 full. Bake at 350°F for 14-16 minutes. Test the cupcakes for doneness by inserting a toothpick into the center of the cupcake. If the toothpick comes out clean, the cupcakes are done. Cool Completely.

For the Frosting

1. Cut the butter into 1-inch blocks. Beat the butter until it’s whipped and fluffy and resembles the spreadable consistency of cream cheese.
2. Then add the cream cheese and cream together for 2-3 minutes until fluffy and free of lumps, scraping down the bowl occasionally.
3. Add the cocoa powder and vanilla extract and beat until well combined. Next, add the confectionary sugar 2 cups at a time, followed by one tablespoon of heavy whipping cream, and beat for 60-90 seconds until completely smooth.
4. Add the remaining powdered sugar and beat until desired consistency, at least 2 minutes. If frosting seems too thin, add an additional ½ cup of powdered sugar at a time. If the frosting seems to thick, add 1 tablespoon heavy cream.
5. Pipe the frosting over the cooled cake and then cover it with sprinkles.