For the cake:

1. Preheat the oven to 350°F.
2. In a large mixing bowl, combine the sugar, vegetable oil, eggs and vanilla extract. Beat on medium speed until the eggs and oil are well incorporated. Next mix in the sour cream and beat until well combined.
3. In a separate bowl, sift together the dry ingredients. Then add half the dry ingredients followed by half of the buttermilk and mix just until the flour starts to incorporate. Then add the remaining dry ingredients, mixing on low speed while pouring in the remaining buttermilk and beating until all of the ingredients are 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. Pour the batter into a 9×13-inch pan and bake at 350°F for 26-28 minutes. Test the cake for doneness by inserting a toothpick into the center of the cake. If the toothpick comes out clean, your cake is done. Remove from the oven and allow to cool completely.

For the frosting:

1. Cut the butter into pieces about 1 tablespoon size. Using the paddle attachment, whip butter for 3-5 minutes, scraping down the bowl occasionally. Beat until butter looks light in color and has more volume.
2. Next, add the cocoa powder and confectionary sugar, followed by two tablespoons of buttermilk and beat for 60-90 seconds until completely smooth.
3. Add the remaining buttermilk and vanilla extract and beat until desired consistency, at least 2 minutes.
4. Spread frosting over cooled cake and then cover with sprinkles. Keep in an airtight container.