Vanilla Sheet Cake Recipe (Costco Copycat!)
This post may contain affiliate links. Please read my disclosure policy.
This Vanilla Sheet Cake Recipe combines tender, moist vanilla cake with a creamy mousse filling and the fluffiest buttercream frosting. Don’t let all the steps fool you — this dessert comes together in just over an hour and is super easy to make. Perfect for birthdays, celebrations, holidays, and special occasions!
Table of Contents
Vanilla Sheet Cake Recipe
No matter how hard I try, the pull of the Costco bakery is just too hard to resist. And once they started selling their sheet cakes by the half-sheet size, it was all over!
Munchkin always asks if we can grab one just because, but I don’t need that grocery bill to be any higher.
Thankfully, it’s easy to replicate at home with this simple vanilla sheet cake recipe!
I’ve been working on all kinds of Costco copycat recipes lately, which means I can skip the prepared section and focus solely on ingredients.
That also means party prep is even easier with dupes of their roll ups, tortellini salad, and chicken bake. Even their chocolate muffins can be made at home!
Ingredient Notes and Substitutions
- Cake Flour – Creates a more tender crumb because it has less protein than all-purpose flour. If you don’t have any, you can make a quick substitute.
Measure out 1 cup of AP flour, then remove 2 tablespoons and replace with 2 tablespoons of cornstarch. Use this mixture in place of 1 cup of cake flour. - Sugar – Use granulated sugar for the cake layers and then powdered sugar for the mousse and buttercream.
- Unsalted Butter – There’s almost 2 full pounds of butter to make this vanilla sheet cake recipe! I like using unsalted so I can control the amount of salt myself.
- Eggs – You’ll need 2 whole eggs plus 8 more egg whites to create a light and fluffy texture in the cake. Save those yolks to make pastry cream later!
- Whole Milk – For richness and flavor, though it helps keep the cake tender as well. It’s in every step of this copycat Costco sheet cake recipe, so make sure you have plenty on hand.
- Heavy Cream – Keep this in the refrigerator until just before whipping for best results. It needs to be super cold to get those stiff peaks!
- Instant Vanilla Pudding – All you need is the powdered mix! It flavors the mousse and helps it set. Substitute with a cheesecake flavor for a richer filling.
Tips and Tricks When Making This Recipe for Vanilla Sheet Cake
- Use the right tools for each layer.
It’s tempting to start mixing and stirring to get this dessert built, but some careful attention makes all the difference!
Whisk together the dry ingredients to help break up any lumps and ensure an even reaction in the batter. Also, sift the powdered sugar for the smoothest buttercream.
The type of mixing bowl doesn’t matter as much for the cake and frosting, but you’ll get the best results using a metal bowl when making the mousse.
Pop the bowl and the beaters in the fridge or freezer for 10 minutes so they’re nice and chilled before getting started.
It’s also much faster to whip heavy cream with the whisk attachment instead of regular beaters, though those will work for everything else.
If using a stand mixer, use the paddle attachment for the cake batter and then the whisk attachment for the mousse and frosting.
- Level the cakes before decorating.
A flat, even surface keeps the mousse from shifting and the cake layers from sliding apart.
Use a cake leveler if you have one… otherwise, a serrated knife will do the trick!
- Chill in stages.
First, make sure the cake layers are completely cool before stacking and decorating.
Once you smooth on the mousse, chill the first cake layer for 10-15 minutes before placing the second one on top. This helps the mousse set and prevents shifting or sliding later.
Frost the entire cake, then chill again before decorating for a firmer base. Pop your copycat Costco sheet cake in the fridge a final time after piping your designs to help the frosting crust over and set.
Prep Ahead
- Soften cream cheese and butter
- Bring eggs to room temperature
- Line and grease cake pans
Kitchen Tools You Will Need
- 9×13 Cake Pans – Use the metal kind with straight edges for cleaner lines, not just any baking dish with rounded edges towards the bottom.
- Parchment Paper – Extra insurance to keep your cake from sticking to the pan!
- Stand Mixer or large mixing bowls with a Hand Mixer to make the batter, mousse filling, and buttercream frosting.
- Serrated Bread Knife – Makes trimming cakes super easy!
- Offset Spatula – This spatula has so many uses and is perfect for smoothing the filling between the cake layers and the frosting on the outside.
Decorating Ideas
For a true copycat Costco sheet cake recipe, you’ll need a piping bag and some decorating tips!
Use a star tip to create a border around the outer edge of the cake or to pipe swirl designs wherever you’d like.
You can even make simple buttercream roses with a star tip or more intricate ones with petal and leaf tips.
And if that’s too complicated, you can never go wrong with edible flowers!
Munchkin loves it when I add sprinkles on top, but if those aren’t your thing, try shaved chocolate or cookie crumbles instead.
Storage and Make-Ahead Tips
Get a jump start by making the sheet cakes and mousse filling a day ahead of time. It’s best to make the buttercream fresh.
Wrap each cake layer tightly in plastic wrap once cool and stack them on the counter. Keep the mousse in the refrigerator until you’re ready to assemble.
Once fully assembled, store your copycat Costco sheet cake in the refrigerator for up to 3 days. It has the best texture and flavor if you let it come to room temperature before serving.
Want to make this recipe for vanilla sheet cake months in advance? By all means! Freeze cooled and wrapped cake layers for up to 3 months, then thaw them overnight in the fridge before decorating.
The buttercream can also be frozen for up to 3 months. Store it in an airtight container, then bring it to room temperature and re-whip before using.
Copycat Costco Sheet Cake FAQ
Start with room temperature ingredients to make mixing easier, and avoid overmixing, as that is guaranteed to create dry, dense cake layers.
Another way to add extra moisture to this vanilla sheet cake recipe is by adding an extra egg yolk or swapping the milk with buttermilk.
Yes! Mix in lemon or orange zest for citrus flavor or cocoa powder for a chocolate version.
If you want it really fruity, add some fresh fruit puree or your favorite preserves. You can also fold in fresh raspberries or strawberries (chop them up first) for a speckled layer.
After adding the powdered sugar, beat the frosting for at least 2 minutes on high speed. A little extra milk will also help smooth it out if it’s not coming together just right.
Just make sure not to add too much liquid, or the buttercream will be too soft for piping.
A pinch of salt goes a long way to balancing the sweetness in frosting! You may hear to simply use less sugar, but that often messes with the consistency of the buttercream itself.
Many commercial bakeries make their buttercream with hi-ratio shortening, which makes it super smooth and fluffy but also super sweet.
Instead, we’re using real butter in this recipe for vanilla sheet cake to create a more balanced flavor.
Enjoy!
With love, from our simple kitchen to yours.
Don’t miss a thing! Follow us on
Facebook | Twitter | Pinterest | Instagram
🍔 Copycat Creations Vol 1
Craving your favorite restaurant meals at home? This exclusive ebook has the boldest, most requested copycat recipes — from fast food faves to sit-down classics.
👉 Buy your copy now and start cooking the meals you love!
Vanilla Sheet Cake Recipe (Costco Copycat!)
Ingredients
For the Vanilla Sheet Cake:
- 5 1/2 cups cake flour
- 4 cups granulated sugar
- 2 tablespoons baking powder
- 1 teaspoon kosher salt
- 1 1/2 cups 3 sticks unsalted butter, softened
- 8 large egg whites
- 2 large whole eggs
- 2 cups whole milk
- 2 teaspoons pure vanilla extract
For the Mousse:
- 1 cup heavy cream, cold
- 8 ounces cream cheese, softened
- 1/2 cup powdered sugar
- 1/2 cup whole milk
- 3.4 ounce package instant vanilla pudding mix
For the Buttercream:
- 2 cups unsalted butter, softened, 4 sticks
- 8 cups powdered sugar
- 2 teaspoons pure vanilla extract
- 6 – 7 tablespoons whole milk, adjust as needed for consistency
Instructions
For the Sheet Cakes:
- Preheat the Oven: Preheat the oven to 350°F. Grease and line two 9×13-inch cake pans with parchment paper.
- Mix the Dry Ingredients: In a large bowl, whisk together the cake flour, sugar, baking powder, and salt.
- Incorporate the Butter: Add the softened butter and mix on low speed until the mixture forms coarse crumbs.
- Add the Eggs: Mix in the egg whites and whole eggs, one at a time, until fully incorporated.
- Finish the Batter: Slowly pour in the milk and vanilla extract, mixing on medium speed until smooth.
- Bake the Cakes: Divide the batter evenly between the pans. Bake for 30–35 minutes, or until a toothpick inserted into the center comes out clean.
- Cool the Cakes: Allow the cakes to cool in the pans for 10 minutes, then transfer to wire racks to cool completely.
For the Mousse:
- Whip the Heavy Cream: In a large bowl, beat the heavy cream on high speed until stiff peaks form. Set aside.
- Blend the Cream Cheese & Sugar: In a separate bowl, beat the cream cheese and powdered sugar until smooth.
- Add the Pudding: Gradually mix in the milk and pudding mix, beating until thickened and smooth.
- Fold in the Whipped Cream: Gently fold the whipped cream into the cream cheese mixture until fully combined. Refrigerate until needed.
For the Buttercream:
- Beat the Butter: In a large bowl, beat the softened butter on medium speed until smooth.
- Incorporate the Sugar & Vanilla: Gradually add the powdered sugar, then mix in the vanilla extract.
- Adjust Consistency: Add milk, one tablespoon at a time, until the frosting reaches a spreadable consistency. Beat on high for 1–2 minutes to make it fluffy.
To Assemble:
- Trim the Cakes: Use a serrated knife to trim any domed tops to create even layers.
- Add the Mousse Layer: Place one cake layer on a serving tray and spread an even layer of mousse over the surface.
- Layer the Cakes: Place the second cake on top, aligning the edges.
- Frost the Cake: Spread the buttercream frosting evenly over the top and sides of the cake.
- Decorate: Use a piping bag with a star tip to create borders or decorative swirls. Top with rainbow sprinkles, shaved chocolate, or crushed cookies if desired.
- Serve: Slice into portions and enjoy!
Donna’s Notes
Nutrition
All nutritional information is based on third party calculations and is only an estimate. Each recipe’s nutritional value will vary depending on the ingredients used, measuring methods, and portion sizes.
Originally uploaded July 2025
Disclosure: Posts may contain affiliate links. If you purchase a product through an affiliate link your price will remain the same and The Slow Roasted Italian will automatically receive a small commission. Thank you for supporting us, it helps us keep creating new recipes.
Welcome!
We’re Donna and Chad, the dream team behind The Slow Roasted Italian. Our focus is on taking complicated OUT of the kitchen. Life is busy enough, making meals should be fast and easy, to help make your life as simple as possible. Read More >>
