Introduction

This Copycat Costco Vanilla Cake is a delightful treat that mirrors the beloved store-bought classic with ease. Soft, moist layers paired with creamy buttercream and mousse make it perfect for any celebration or a special dessert at home.

The image shows a two-layer white cake with smooth white frosting, decorated with blue and pink piped swirls and small pearl-like accents on the edges and top. Two slices are served on white plates with a delicate gray pattern around the rims, each slice showing the light yellow cake layers separated by white cream filling. Each slice has blue and pink frosting details on the edge of the top and a silver fork beside it. The cake sits on a white scalloped cake stand, placed on a soft white marbled textured surface with scattered small colorful candy bits and twisted candles nearby. Photo taken with an iphone --ar 4:5 --v 7

Ingredients

2 1/2 cups plus 2 tablespoons cake flour
1 1/2 cups plus 2 tablespoons granulated sugar
1 tablespoon baking powder
3/4 teaspoon fine salt
3/4 cup unsalted butter, very soft
4 large egg whites, room temperature
1 large egg yolk, room temperature
1 tablespoon vanilla extract
1 cup buttermilk, room temperature

Buttercream Ingredients

2 tablespoons water
2 tablespoons cornstarch
1 cup unsalted butter, very soft
1/2 cup vegetable shortening, room temperature
4 cups powdered sugar
1/2 teaspoon fine salt
1 tablespoon vanilla extract
3 to 4 tablespoons whole milk or heavy cream, room temperature

Assembly Additions

Copycat Costco Vanilla Mousse
Sprinkles

Instructions

Step 1: Preheat your oven to 350°F. Spray two 8-inch cake pans with baking spray, line the bottoms with parchment paper, then set aside.
Step 2: In a large bowl, combine the cake flour, granulated sugar, baking powder, and salt.
Step 3: Using a mixer on low speed, gradually add the softened butter to the dry ingredients. The mixture will resemble a sandy texture. Continue to beat for 1 to 2 minutes, scraping the bowl’s sides and bottom.
Step 4: Gradually beat in the egg whites one at a time, followed by the egg yolk and vanilla extract.
Step 5: On low speed, add the buttermilk in three additions, mixing 1 to 2 minutes after each addition until fully incorporated.
Step 6: Divide the batter evenly between the prepared cake pans. Bake for 26 to 30 minutes or until the cakes are golden on top and a toothpick inserted comes out mostly clean with a few moist crumbs.
Step 7: Allow the cakes to cool in the pans for 5 minutes, then invert them onto wire racks to cool completely. Remove parchment paper. For best results, wrap the cooled cakes in plastic wrap and refrigerate if assembling the next day.
Step 8: To make the buttercream, whisk together water and cornstarch in a small bowl and set aside.
Step 9: In a large bowl, beat the butter and shortening until light and fluffy, about 3 to 4 minutes. Scrape down the bowl.
Step 10: Mix in the cornstarch mixture, then gradually add powdered sugar on low speed, scraping the bowl as needed.
Step 11: Add salt and vanilla extract. If the frosting is too thick, add milk one tablespoon at a time until desired consistency is reached.
Step 12: When ready to assemble, level the cakes with a serrated knife if domed. Secure the first layer onto a cake board with a dab of frosting.
Step 13: Pipe a ring of buttercream around the edge of the first layer, then fill the center with vanilla mousse.
Step 14: Place the second cake layer on top.
Step 15: Coat the entire cake with remaining buttercream, smoothing and removing excess with an offset spatula.
Step 16: Decorate with sprinkles, slice, and enjoy!

Tips & Variations

For softer cake layers, ensure all wet ingredients are at room temperature before mixing.
Use cake flour for the lightest, tenderest texture; substitute with all-purpose flour plus cornstarch if needed.
Chill the cake layers before frosting to make assembly easier and reduce crumbs in the buttercream.
Add a splash of almond extract to the batter for a subtle nutty twist.

Storage

Store the fully assembled cake covered in the refrigerator for up to 4 days. Bring to room temperature before serving for the best flavor and texture. Leftover plain cake layers (without frosting) can be wrapped tightly and frozen for up to 2 months.

How to Serve

A close-up of a slice of two-layer yellow cake with white creamy frosting between the layers and covering the outside, sitting on a white plate with pink floral designs. The cake layers are moist and light yellow, with smooth, thick frosting that slightly drapes down the sides. Behind the cake, there is a swirl of light blue whipped decoration topped with small colorful sprinkles. A shiny silver fork rests on the plate in front of the cake. The background features a soft white marbled texture. photo taken with an iphone --ar 4:5 --v 7

Serve this delicious recipe with your favorite sides.

FAQs

Can I make the cake layers ahead of time?

Yes, the cake layers can be baked a day or two in advance. Wrap them tightly in plastic wrap and refrigerate until ready to frost and assemble.

What can I use instead of buttermilk?

If you don’t have buttermilk, mix 1 tablespoon of lemon juice or white vinegar with enough milk to make 1 cup. Let it sit for 5 minutes before using.