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Copycat Costco Vanilla Cake

Copycat Costco Vanilla Cake

If you know, you know. A vanilla-infused cake with a cheesecake-like vanilla mousse and sweet vanilla buttercream form a cake that doesn’t need a party to devour. The happy birthday message written on top is merely a ruse to disguise the reality that it’s just for you (maybe a tiny bit for your family) on a weekday night. The membership restraint is lifted with this Copycat Costco Vanilla Cake. A homemade version of a popular cake that’s satisfying through and through.

Ingredients
For the Cake:
  • 2 1/2 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
For the Buttercream:
  • 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
For Assembling the Cake:
  • Copycat Costco Vanilla Mousse
  • Sprinkles

Instructions
To make the Cake:
  1. Preheat oven to 350°F. Spray 2 8-inch cake pans with baking spray, line the bottoms with parchment paper, set aside.
  2. In a large bowl combine cake flour, granulated sugar, baking powder, and salt.
  3. With the mixer on low speed gradually add in the butter. Once all of the butter is combined, it’ll look like a sandy mixture, in warmer climates it’ll look softer, both are fine.
  4. Continue to beat the batter for 1 to 2 minutes. Scrape the sides and bottom of the bowl.
  5. Gradually the egg whites, one at a time, beating well after each addition. Beat in egg yolk. Add in vanilla.
  6. In the mixer on a low speed, gradually add the buttermilk in 3 additions, beating 1 to 2 minutes after each addition.
  7. Divide batter evenly between prepared pans, baking until cakes are golden on top and a toothpick inserted comes out mostly clean with a few moist (not wet) crumbs. About 26 to 30 minutes.
  8. Let cake layers cool in pans for 5 minutes before inverting onto a wire rack to cool completely. Remove parchment paper.
  9. If assembling the next day, wrap cooled cakes in plastic wrap and refrigerator until ready to assemble.
To make the Buttercream:
  1. In a small bowl combine water and cornstarch, whisking to combine, set aside.
  2. In a large bowl beat butter and shortening until light and fluffy, about 3 to 4 minutes. Scrape the sides and bottom of the bowl.
  3. Add in the cornstarch mixture, mixing to combine.
  4. On a low speed, gradually add the powdered sugar, scraping the sides and bottom of the bowl as needed.
  5. Add in salt and vanilla. If the frosting is looking too thick, add in some milk, one tablespoon at a time.
To assemble the cake:
  1. If the cakes have domes use a serrated knife to level off the cakes. Place a bit of frosting onto a cake board and secure the first cake layer onto the board.
  2. Add some of the frosting into a pastry bag. Pipe a ring on the perimeter of the cake layer.
  3. Fill the ring with the mousse filling.
  4. Top with the second cake layer.
  5. Coat the outside of the cake with buttercream, using an offset spatula to remove the excess frosting. Decorate cake with the remaining frosting.
  6. Garnish with sprinkles, slice, and enjoy!