Copycat Costco Sheet Cake is a delightful, nostalgic dessert that captures the essence of cheerful celebrations and special occasions. This cake is fluffy, creamy, and utterly indulgent, making it a wonderful treat for family gatherings, birthday parties, or simply when you’re in need of some comfort food. The great news is that this Copycat Costco Sheet Cake recipe is incredibly easy to follow, providing you with a step-by-step guide that ensures even novice bakers can achieve that bakery-quality finish right at home. Whip up this cake and watch as it transforms any ordinary day into a festive occasion!

Ingredients

Let’s indulge in the ingredients that make this Copycat Costco Sheet Cake a showstopper. Each component plays a crucial role in creating a perfectly moist and delicious dessert.

Cooking spray – a must for easy removal post-baking.
2 (15.25-oz.) boxes of white cake mix (Pillsbury) – these mixes yield a fluffy, pliable cake that is a dream to bite into.
1/2 tsp. kosher salt – a little salt enhances sweetness and balances flavors.
8 large egg whites – giving a tender crumb that elevates the cake’s texture.
1 1/2 cups sour cream – introduces a rich creaminess that enhances moisture.
1 cup whole milk – adds another layer of creaminess, making every mouthful delicious.
2/3 cup vegetable oil – ensures a tender, moist finish.
2 tsp. pure vanilla extract (preferably clear) – fragrant, pure vanilla uplifts the cake’s flavor beautifully.
1 (8-oz.) pkg. cream cheese, room temperature – lays the foundation for the luscious cheesecake mousse.
1/2 cup confectioners’ sugar – provides sweetness and velvety texture for the mousse.
1/2 tsp. kosher salt – balances out the sweetness perfectly.
1 cup whole milk – essential for achieving that creamy mousse consistency.
1 (3.4-oz.) pkg. vanilla instant pudding – thickens the mousse, giving it a delightful structure.
1 cup heavy cream – a key ingredient for that rich, whipped texture.
2 cups vegetable shortening (such as Crisco) – needed for the frosting, giving it that smooth, spreadable nature.
1/2 cup water – keeps the frosting components well-blended.
1 Tbsp. pure vanilla extract (preferably clear) – adds another layer of pure vanilla richness.
3/4 tsp. kosher salt – contributes to the overall flavor.
8 cups confectioners’ sugar, divided – sweetness overload!
Sprinkles, for decorating (optional) – because who doesn’t love a splash of color?

Cooking Time & Tips for Copycat Costco Sheet Cake

Cooking this Copycat Costco Sheet Cake is both quick and rewarding! You can have this cake ready in just over an hour, making it a fantastic option for those spontaneous gatherings. Quick preparation involves mixing your ingredients together and baking, while the slow preparation enables you to master the frosting and assembly techniques for a more refined finish.

For optimal success, here are a few practical tips: be sure to preheat your oven well before starting to mix your batter; this ensures even baking. Also, allow the cakes to cool completely before trimming the tops to achieve perfectly even layers. Don’t rush the frosting; letting your cream cheese come to room temperature ensures a smooth consistency.

Step-by-Step Directions

Get ready to turn your kitchen into a sweet-smelling bakery with these engaging step-by-step directions for your Copycat Costco Sheet Cake!

Preheat your oven to 350 degrees Fahrenheit, setting the stage for a perfectly baked cake.
Grease and line two 13×9 metal baking pans with parchment paper—this step ensures easy release post-baking.
In a large bowl, whisk the cake mix and salt together, combining dry ingredients to achieve a well-balanced flavor.
Add in the egg whites, sour cream, milk, vegetable oil, and pure vanilla extract. Beat the mixture until fully combined, letting your mixer do the work until it’s smooth and creamy.
Divide the batter evenly between the prepared pans, spreading it out evenly for uniform baking.
Bake for 20-25 minutes or until a toothpick inserted into the center comes out clean. The aroma of freshly baked cake will fill your kitchen!
Allow the cakes to cool fully before trimming the tops for even layers. Patience makes for perfect layers!

Now onto the show-stopping Vanilla Cheesecake Mousse:
8. In a separate bowl, beat together the cream cheese, confectioners’ sugar, and salt until smooth and creamy.
9. Gradually add in the milk and vanilla pudding mix, mixing until fully incorporated—a luscious mixer of flavors.
10. Add the heavy cream, then whip until thickened, bringing a light and airy texture to the mousse.

For the frosting:
11. Beat together the vegetable shortening, water, vanilla, and salt in another bowl until smooth and creamy.
12. Gradually add the confectioners’ sugar, mixing until fluffy and delightful—the perfect finish for your cake.

To assemble your cake:
13. Start with one layer of cake on a serving platter, add a generous layer of mousse on top, and then place the second layer of cake on top.
14. Frost the top and sides of the cake with the creamy frosting, making it as smooth and elegant as possible.
15. Get creative! Decorate with sprinkles for that festive finish, making your Copycat Costco Sheet Cake come alive!

Serving Suggestions & Occasions

This Copycat Costco Sheet Cake is perfect for virtually any occasion! Serve it at birthday parties, bridal showers, or family get-togethers to delight guests of all ages. Pair it with a scoop of vanilla ice cream for an extra touch of indulgence or serve alongside fresh fruit for a refreshing contrast. The cake’s vibrant appearance allows it to steal the show, making it a centerpiece dessert fit for celebrations!

Common Mistakes for Copycat Costco Sheet Cake

While this recipe is straightforward, avoiding a few common pitfalls can elevate your baking game! First, don’t overlook the importance of accurate measurements; too much or too little of an ingredient can dramatically change your cake’s texture. Also, ensure your ingredients are at room temperature, especially the cream cheese and eggs, for the creamiest, most cohesive batter and frosting. Lastly, remember to let the cakes cool completely before frosting; this will prevent the frosting from melting or sliding off the cake layers.

Healthier Alternatives & Variations

Looking for a twist? While the classic Copycat Costco Sheet Cake is undeniably delicious, you can easily make healthier alternatives. Substitute the white cake mix for whole wheat or gluten-free cake mix for a lighter option. Use Greek yogurt in place of sour cream for added protein, and opt for low-fat cream cheese. You might also consider reducing the sugar content or substituting with a natural sweetener, such as honey or maple syrup.

FAQs

Can I use a different flavor of cake mix?
Absolutely! Feel free to try chocolate or lemon cake mix for different flavor profiles.
How long does the cake last?
The cake stays fresh for about 3 days in the refrigerator when covered properly.
Can I freeze the cake?
Yes! Wrap it tightly and store it in the freezer for up to 2-3 months.
Can I make this cake ahead of time?
Certainly! You can prepare the layers a day in advance and assemble the cake when you’re ready to serve.
Is there a dairy-free option?
Yes! Substitute all dairy ingredients with plant-based alternatives to cater to dietary needs.
What happens if I over-mix the batter?
Over-mixing can result in a dense cake, so make sure to mix just until combined.

Conclusion

Don’t wait any longer to bring this Copycat Costco Sheet Cake into your kitchen! With its easy-to-follow steps and delightful bursts of flavor, it’s sure to leave a lasting impression on everyone who tastes it. Whether for a celebration or simply to indulge yourself, this cake is a guaranteed crowd-pleaser. So gather your ingredients, ignite your love for baking, and let this beautiful dessert brighten your day!

Homemade Costco sheet cake recipe with frosting and decorations

Copycat Costco Sheet Cake

A fluffy, creamy dessert perfect for celebrations, this Copycat Costco Sheet Cake is easy to make and tastes just like the original.

Print Recipe Pin Recipe

Prep Time 15

Cook Time 25

Total Time 40

Course Cake, Dessert

Cuisine American

Servings 24 pieces

Calories 350 kcal

Ingredients

For the cake

2 boxes 2 (15.25-oz.) boxes of white cake mix (Pillsbury) Yields a fluffy, pliable cake.
1/2 tsp 1/2 tsp. kosher salt Enhances sweetness.
8 large 8 large egg whites Provides a tender crumb.
1 1/2 cups 1 1/2 cups sour cream Enhances moisture.
1 cup 1 cup whole milk Adds creaminess.
2/3 cup 2/3 cup vegetable oil Ensures a moist finish.
2 tsp 2 tsp. pure vanilla extract (preferably clear) Uplifts flavor.

For the mousse

1 pkg. 1 (8-oz.) pkg. cream cheese, room temperature Foundation for the mousse.
1/2 cup 1/2 cup confectioners’ sugar Adds sweetness.
1/2 tsp 1/2 tsp. kosher salt Balances sweetness.
1 cup 1 cup whole milk For creamy consistency.
1 pkg. 1 (3.4-oz.) pkg. vanilla instant pudding Thickens the mousse.
1 cup 1 cup heavy cream For rich texture.

For the frosting

2 cups 2 cups vegetable shortening (such as Crisco) For a smooth frosting.
1/2 cup 1/2 cup water Keeps frosting blended.
1 Tbsp. 1 Tbsp. pure vanilla extract (preferably clear) Adds richness.
3/4 tsp 3/4 tsp. kosher salt Enhances flavor.
8 cups 8 cups confectioners’ sugar, divided Adds sweetness.
to taste Sprinkles, for decorating (optional) For a festive finish.

Instructions

Preparation

Preheat your oven to 350°F (175°C).
Grease and line two 13x9 metal baking pans with parchment paper.
In a large bowl, whisk the cake mix and salt together.
Add in the egg whites, sour cream, milk, vegetable oil, and pure vanilla extract. Beat until combined.
Divide the batter evenly between the prepared pans.

Baking

Bake for 20-25 minutes or until a toothpick inserted in the center comes out clean.
Allow the cakes to cool completely before trimming the tops for even layers.

Making the Mousse

In a separate bowl, beat together the cream cheese, confectioners’ sugar, and salt until smooth.
Gradually add in the milk and vanilla pudding mix, mixing until fully incorporated.
Add the heavy cream and whip until thickened.

Making the Frosting

Beat together the vegetable shortening, water, vanilla, and salt until smooth.
Gradually add the confectioners’ sugar, mixing until fluffy.

Assembly

Start with one layer of cake on a serving platter, add a layer of mousse on top, and place the second layer of cake on top.
Frost the top and sides of the cake with the creamy frosting.
Decorate with sprinkles if desired.