Costco Chocolate Cake Recipe
This Costco Chocolate Cake recipe features rich layers of moist chocolate cake, a creamy chocolate mousse filling, and fluffy chocolate buttercream frosting. The cake is made with basic pantry ingredients, including cocoa powder, flour, sugar, eggs, and milk. Easy to assemble and chill before serving, it’s a decadent homemade version of the beloved Costco classic, perfect for any special occasion.
Equipment
- 2 x 9-inch round cake pans
- Mixing bowls
- Electric mixer or whisk
- Measuring cups and spoons
- Rubber spatula
- Saucepan or kettle (for boiling water)
- Cooling rack
- Serrated knife or cake leveler
- Offset spatula or frosting knife
Ingredients
For the Chocolate Cake:
- 1¾ cups all-purpose flour
- 1½ cups granulated sugar
- ¾ cup unsweetened cocoa powder
- 1½ teaspoons baking powder
- 1½ teaspoons baking soda
- 1 teaspoon salt
- 2 large eggs
- 1 cup whole milk
- ½ cup vegetable oil
- 2 teaspoons vanilla extract
- 1 cup boiling water
Chocolate Mousse Filling:
- 5.9 oz instant chocolate pudding mix
- 3 cups heavy whipping cream
Chocolate Frosting:
- 1 cup unsalted butter softened
- 3½ cups powdered sugar
- ½ cup unsweetened cocoa powder
- ½ cup heavy cream
- 2 teaspoons vanilla extract
- Pinch of salt
Instructions
Pan Prep and Oven Heat
- Set the oven to 350°F (175°C). Grease and flour two 9-inch round cake pans, or line them with parchment paper for easy removal after baking.
Mix Dry Ingredients
- In a large bowl, whisk together flour, sugar, cocoa powder, baking powder, baking soda, and salt until fully combined.
Add Wet Ingredients
- Add eggs, milk, oil, and vanilla to the dry mixture. Beat with an electric mixer on medium speed for about 2–3 minutes until the batter is smooth.
Add Boiling Water
- Slowly stir in boiling water. The batter will be thin—this is expected. Mix until just blended, then pour evenly into the two pans.
Bake the Cakes
- Bake for 30–35 minutes, or until a toothpick inserted in the center comes out clean. Let the cakes cool in the pans for 10 minutes, then transfer them to a wire rack to cool completely.
Make the Mousse Filling
- In a large bowl, beat instant chocolate pudding mix with heavy cream on high speed until thick and mousse-like, about 3–4 minutes. Keep chilled until needed.
Prepare the Frosting
- In another bowl, beat softened butter until smooth. Gradually add powdered sugar and cocoa powder while mixing on low. Add heavy cream, vanilla, and a pinch of salt, then beat on medium-high until fluffy about 4–5 minutes.
Assemble the Cake
- Level cake layers if needed. Place one layer on a serving plate, spread with mousse, then place the second layer on top. Cover the cake with frosting, smoothing the top and sides. Chill for 30 minutes before slicing.
Notes
For an extra touch, you can add chocolate shavings or sprinkles on top of the frosting. To make the cake even richer, consider incorporating a layer of chocolate ganache between the cake layers or using a flavored liqueur in the cake batter for added depth.