Description

This Copycat Costco Sheet Cake recipe recreates the beloved sheet cake with its moist, fluffy vanilla cake base, topped with a rich and creamy vanilla cheesecake mousse, and finished with a luxurious bakery-style frosting. Perfect for large gatherings, this cake combines the soft texture of a classic sheet cake with a luscious, velvety frosting and an optional sprinkle decoration for a festive touch.

Ingredients

Scale

Cake

Cooking spray
2 (15.25-oz.) boxes white cake mix (we used Pillsbury)
1/2 tsp. kosher salt
8 large egg whites
1 1/2 c. sour cream
1 c. whole milk
2/3 c. vegetable oil
2 tsp. pure vanilla extract (preferably clear)

Vanilla Cheesecake Mousse

1 (8-oz.) pkg. cream cheese, room temperature
1/2 c. (57 g) confectioners’ sugar
1 (3.4-oz.) pkg. vanilla instant pudding
1 c. heavy cream

Bakery-Style Frosting & Assembly

2 c. vegetable shortening (such as Crisco)
1/2 c. water
1 tbsp. pure vanilla extract (preferably clear)
3/4 tsp. kosher salt
8 c. (904 g) confectioners’ sugar, divided
Sprinkles, for decorating (optional)
A piping bag, a star tip

Instructions

Prepare the Cake Batter: Preheat your oven and grease the baking pan lightly with cooking spray. In a large mixing bowl, combine the two boxes of white cake mix with kosher salt, egg whites, sour cream, whole milk, vegetable oil, and vanilla extract. Mix on medium speed until the batter is smooth and well combined.
Bake the Cake: Pour the batter evenly into the prepared sheet cake pan and bake according to the package instructions for the cake mix, usually about 25 to 35 minutes, or until a toothpick inserted in the center comes out clean. Allow the cake to cool completely in the pan on a wire rack before frosting.
Make the Vanilla Cheesecake Mousse: In a large bowl, beat the softened cream cheese until smooth. Add the confectioners’ sugar and vanilla instant pudding mix and combine thoroughly. Slowly add the heavy cream and whip the mixture until thick and fluffy, resembling a mousse texture. Keep chilled until ready to assemble.
Prepare the Bakery-Style Frosting: In a large bowl, combine vegetable shortening, water, vanilla extract, and kosher salt. Gradually add half of the confectioners’ sugar, mixing well to incorporate. Then, add the remaining confectioners’ sugar in portions, beating the frosting until it is light and fluffy and reaches a creamy spreadable consistency.
Assemble the Cake: Spread the cheesecake mousse evenly over the completely cooled cake layer. Then, generously frost the top and sides of the cake with the bakery-style frosting using a spatula for smooth coverage. Decorate with sprinkles if desired and use a piping bag fitted with a star tip to add decorative designs. Refrigerate the cake for at least one hour before serving to allow the mousse and frosting to set properly.

Notes

Ensure the cake is fully cooled before applying the mousse to prevent it from melting.
Use clear vanilla extract to maintain the cake’s bright white color.
Room temperature cream cheese whips more easily, resulting in a smoother mousse.
Refrigerate leftover cake tightly covered to maintain freshness for up to 4 days.

Prep Time: 30 minutes
Cook Time: 35 minutes
Category: Dessert
Method: Baking
Cuisine: American

Keywords: Costco sheet cake, white sheet cake, vanilla cheesecake mousse, bakery frosting, copycat cake recipe