Preheat oven to 325°F. Prep your cake rounds by covering the inside of the pans with a light layer of butter and then dusting with flour. I like to use my fingers to make sure the butter gets in all seams.

Mix together, either by hand or in a stand mixer, the oil, vanilla, sour cream, heavy cream and egg whites. Then mix in the boxed cake mix. Divide the batter between the 3 cake rounds.

Bake for 25 minutes or until a toothpick inserted comes out clean. Make sure to bake all the cakes on the same oven rack so they bake evenly.

Let the cakes cool for 5 minutes then flip upside down onto a wire cooling rack and remove the pans. They should come out easily.

Let the cakes cool completely before frosting.