Combine room temperature butter, vegetable oil, sugar, and vanilla extract in a mixing bowl. Mix on medium speed or whisk by hand until well combined.

Add buttermilk and mix until combined. Sift in the flour, baking powder, and salt, mixing on low speed just until the batter comes together.

In a separate bowl, whip the egg whites from low to high speed until stiff peaks form. Gently fold half the egg whites into the batter to keep it light and airy, then fold in the rest.

Chop the Oreos roughly and add them to the batter along with sprinkles. Prepare your pans using the techniques described in How to prep your cake pans.

Pour batter into prepared pans and bake at 165°C (330°F) for 35 to 40 minutes, until a toothpick inserted comes out clean.

Cool the cakes slightly before removing from pans. Fill and decorate with Chocolate Swiss Meringue Buttercream, vanilla buttercream, a yellow white chocolate drip, more Oreos, and sprinkles.