White Cake with Vanilla Buttercream - Baking with Blondie

For the White Cake: Preheat oven to 325 degrees. Prep 3 6″ cake rounds (or 2 8″ cake rounds) with a wipe of shortening and dust of powdered sugar. Set aside.In a large bowl, whisk together the sour cream, buttermilk, vanilla, egg whites, and vegetable oil until thoroughly combined.Sift in the white cake mix. Stir until just combined (don’t overmix!), then divide between prepared cake rounds.Bake for 25-27 minutes until center is baked through (don’t overbake!). Remove from oven, let cool in pan for 5 minutes, then flip out onto a cooling rack until room temperature. I usually wrap mine in plastic wrap and freeze for at least a day before frosting.[br]For the buttercream: In a stand mixer fitted with a paddle attachment, whip up the butter until it’s light and fluffy. Scrape down the sides, then add in the vanilla, paste, salt, and heavy cream.Slowly add in the powdered sugar until you’re desired consistency is reached. Add in more heavy cream if you want to thin it out.Turn mixer on a high speed for 2 minutes and whip up the buttercream until it’s light and fluffy and lighter in color. Turn the mixer to the lowest speed for about 30 seconds to beat out any air bubbles. Hand stir with a wooden spoon to further beat out any air bubbles.[br]Assembly: Tape a 6″ cardboard cake board to a 8″ cake board and place onto a turntable.Pipe on a little buttercream in the center and spread around to act as glue for the first cake round.Place on the first cake round in the center, then pipe on about a 1/4 inch layer of buttercream. Add on the next cake round and repeat.Crumb coat the cake, then freeze for at least 10 minutes.Add on the final coat, press sprinkles onto the bottom rim of the cake. Hand place any little sprinkles up the sides.Using a 1M Wilton piping tip, pipe on swirls on the top, and top with additional sprinkles.