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Vanilla Sheet Cake

This soft and sweet vanilla sheet cake replicates the popular Costco cake, featuring a light mousse layer and classic buttercream, perfect for any occasion.
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Prep Time 30 minutes
Cook Time 35 minutes
Total Time 1 hour 5 minutes
Servings: 24 servings
Course: Cake, Dessert
Cuisine: American
Calories: 450
Ingredients Method Notes

Ingredients
  

Cake Ingredients
  • 5.5 cups cake flour
  • 4 cups granulated sugar
  • 2 tablespoons baking powder
  • 1 teaspoon kosher salt
  • 1.5 cups unsalted butter, softened
  • 8 large egg whites use room temperature
  • 2 large whole eggs use room temperature
  • 2 cups whole milk use room temperature
  • 2 teaspoons pure vanilla extract
Mousse Ingredients
  • 1 cup heavy cream, cold needed for whipping
  • 8 ounces cream cheese, softened
  • 0.5 cups powdered sugar
  • 0.5 cups whole milk
  • 3.4 ounce package instant vanilla pudding mix
Buttercream Ingredients
  • 2 cups unsalted butter, softened
  • 8 cups powdered sugar
  • 2 teaspoons pure vanilla extract
  • 6-7 tablespoons whole milk adjust as needed for consistency

Method
 

Preparation
  1. Preheat the oven to 350°F (177°C). Grease and line two 9x13 inch cake pans with parchment paper.
  2. In a large bowl, whisk together the cake flour, sugar, baking powder, and salt. Mix in the softened butter until coarse crumbs form.
  3. Add egg whites and whole eggs one at a time, mixing fully after each addition. Slowly add milk and vanilla, mixing until smooth.
  4. Divide batter into pans and bake for 30 to 35 minutes, or until a toothpick comes out clean. Cool for 10 minutes in pans before transferring to wire racks.
For the Mousse
  1. Beat heavy cream until stiff peaks form and set aside.
  2. In another bowl, beat cream cheese and powdered sugar until smooth. Gradually add milk and pudding mix; beat until thickened.
  3. Fold in whipped cream and refrigerate until needed.
For the Buttercream
  1. Beat softened butter until smooth, then gradually mix in powdered sugar and vanilla extract. Adjust consistency with milk, if necessary.
  2. Beat on high for 1-2 minutes.
To Assemble
  1. Trim any domed tops off cakes to create even layers.
  2. Spread mousse on top of one cake layer, then place the second layer on top.
  3. Frost the cake with buttercream.
  4. Decorate using a piping bag and toppings like sprinkles or chocolate, if desired.
Serving Suggestions
  1. Serve slices on a simple plate, keeping slices small as the cake is rich.
  2. Pair with fresh berries or a dollop of whipped cream.
  3. Consider pairing with coffee or espresso drinks for adult gatherings.

Notes

Store the cake covered in the fridge for up to 5 days. For longer storage, freeze portions wrapped in plastic wrap and foil. Allow to come to room temperature before serving.