2tablespoonsheavy cream (you may need more depending on the thickness)
pastel colored sprinkles
Instructions
Preheat the oven to 350°F and spray a 9x13-inch baking dish with nonstick cooking spray
In a large mixing bowl, use an electric mixer to combine 15.25 ounce box white cake mix, ¼ cup water, 4 egg whites, ½ cup vegetable oil, 1 cup sour cream and 1-2 teaspoons clear vanilla extract. Mix on low speed for 30 seconds or until combined. Scrape the edges of the bowl. Beat on medium speed for 2 minutes more, scraping the edges occasionally.
Pour 2 cups of the batter into the prepared pan.
Divide the remaining batter between 3 medium bowls (about ½ cup each). Add a few drops of blue, pink, and yellow food coloring (one color per bowl) to the batter, stirring well after each drop, until the batter reaches the desired color.
Place spoonfuls of each colored batter in random places on top of the white batter already in the baking dish.
Run a butter knife back and forth through the batter to swirl the added color.
Bake cake for 30-35 minutes or until an inserted toothpick comes out clean.
With an electric mixer, whip ½ cup butter, softened to room temperature until it is lighter in color and a bit fluffy.
Add in 2 cups powdered sugar and ¼ teaspoon salt. Beat on low to medium speed for about 1 minute until well combined, occasionally scraping the sides of the bowl.
Add in 1 ½ teaspoons vanilla extract and 2 tablespoons heavy cream and beat for one minute. Slowly add more heavy cream, if necessary, to get the desired consistency. Whip for 1 more minute or until light and fluffy.
Frost and decorate the cake with pastel colored sprinkles.
Notes
You can use a homemade white cake if you'd like.
Whole eggs can be used, see my tips above.
Milk can be used instead of heavy cream
This can be frozen, again see tips above.
Change up your food coloring for different holidays.