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image of a slice of dark chocolate tuxedo mousse cake on a plate
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4.84 from 120 rating

Tuxedo Cake (Costco Copycat!)

This tuxedo cake is my take on the Costco tuxedo cake! It's made with dense, fudgy chocolate cake layers, filled with fluffy dark chocolate and white chocolate mousse, and topped with rich chocolate ganache frosting.
Prep Time30 minutes
Cook Time25 minutes
Additional Time2 hours 30 minutes
Total Time3 hours 25 minutes
Course: Cakes
Cuisine: American
Servings: 24
Calories: 466kcal
Author: Chelsey White

Equipment

Ingredients

Dark and White Chocolate Mousse

  • 1/2 cup or 4 oz. good quality dark chocolate chips 90g
  • 1/3 cup water, warm 80ml
  • 1/4 cup dark or Dutch-processed cocoa powder 25g
  • 3/4 cup good quality white chocolate chips 130g
  • 2 1/3 cups cold heavy whipping cream, divided 560ml
  • 1/4 cup powdered sugar 30g
  • 2 tsp vanilla extract or vanilla bean paste 8ml
  • 1/2 tsp fine salt 3g

Chocolate Ganache Frosting

  • 3/4 cup heavy whipping cream, room temperature 180g
  • 1 cup dark (60-65% cocoa) chocolate chips 175g
  • 2 Tbsp unsalted butter, room temperature 30g
  • 1 Tbsp light corn syrup - optional 20g
  • 1/4 tsp fine salt 2g

Dark Chocolate Cake

  • 2 1/2 cups granulated sugar 500g
  • 2 1/4 cups all-purpose flour 280g
  • 3/4 cup dark or Dutch-processed cocoa powder 75g
  • 2 1/2 tsp baking powder 10g
  • 1 tsp fine salt 6g
  • 1 cup unsalted butter, room temperature 226g
  • 1 cup carton egg whites or 7 large egg whites, room temperature 240g
  • 1 1/2 cups buttermilk, room temperature 360g
  • 2 Tbsp vegetable or canola oil 30g
  • 2 tsp vanilla extract or vanilla bean paste 8g
  • 1 tsp instant espresso - optional

Chocolate Simple Syrup - Optional

  • 1/2 cup water 120g
  • 1/2 cup granulated sugar 100g
  • 1 Tbsp unsweetened cocoa powder, sifted 8g

Instructions

Dark and White Chocolate Mousse Filling

  • Make the mousse first, so it has time to chill. Or better yet, make this mousse in advance! It can be made 1-2 days ahead of time.
  • Place a large mixing bowl and hand mixer beaters or the bowl of a stand mixer and whisk attachment in the freezer. This makes it easier and quicker to whip up the whipped cream for the mousse.
  • Melt 1/2 cup of dark chocolate chips in a medium-sized, heat-proof bowl. Heat in 20-30 second increments in the microwave, stirring after each interval until the chocolate is completely melted and smooth. You can also use a double boiler if you don't have a microwave.
  • In a small bowl, whisk together 1/3 cup of warm water and 1/4 cup of dark cocoa powder. Pour into the melted dark chocolate and whisk together until smooth. The mixture should be somewhat thick. Set aside.
  • Add 3/4 cup of white chocolate chips and 1/3 cup of heavy cream to a medium-sized, heat-proof bowl. Heat for 45-60 seconds in the microwave, then let the mixture sit for a minute. Stir until combined with a rubber spatula. The white chocolate should be completely melted, and the mixture should be smooth. You can also use a double boiler if you don't have a microwave. Set aside.
  • Then pour 2 cups of heavy cream, 1/4 cup of powdered sugar, 2 tsp of vanilla extract or vanilla bean paste, and 1/2 tsp of fine salt into a large bowl, or the bowl of a stand mixer fit with a whisk attachment.
  • Mix on medium-high speed until the whipped cream starts to gather in the whisk attachment and you can see texture around the edges of the bowl. The whipped cream should be thick and able to keep its shape. This usually takes about 2 1/2 to 3 minutes in my stand mixer.
  • Scoop half of the whipped cream into a separate bowl, and mix in the chocolate/cocoa/water mixture using a rubber spatula. Use the spatula to swoop around the sides of the bowl and pull through the center until the ingredients are fully combined. Be careful not to over-mix the mousse, or it will become deflated and lose its structure.
  • Pour the melted white chocolate/heavy cream mixture into the remaining whipped cream and fold together using a rubber spatula. At this point, the white chocolate mixture should have cooled down a bit and should still be fluid, but not hot to the touch. Use the spatula to swoop around the sides of the bowl and pull through the center. Be careful not to over-mix the mousse, or it will become deflated and lose its structure.
  • Cover both bowls of mousse with plastic wrap or scoop each mousse into its own piping bag and chill in the refrigerator for at least 2 hours.

Chocolate Ganache Frosting

  • Make the chocolate ganache next, because it needs time to cool and thicken before it's used to frost this cake.
  • Heat 3/4 cup of heavy cream in a heatproof bowl in the microwave for 45 seconds, until it's just beginning to bubble.
  • Gently pour 1 cup of dark chocolate chips into the heavy cream. Make sure the chips are fully covered with cream. Let the mixture sit for 1 minute.
    If you want to use milk chocolate to make the ganache, use 1/3 cup (80g) of heavy cream and 1 1/3 cups (240g) of milk chocolate.
  • Stir slowly until the cream and chocolate combine and the mixture is smooth. If any bits of chocolate aren't fully melted, heat the mixture again for 15 seconds and stir until smooth.
  • Mix in 2 Tbsp of room temperature unsalted butter, 1 Tbsp corn syrup, and 1/4 tsp fine salt until combined.
  • Cover with plastic wrap to prevent the ganache from forming a skin, then set aside to cool to room temperature. If you're in a rush, pour the ganache into a wide, shallow container to help it cool down faster. If you need to make this in advance, it can be covered and stored in the fridge for up to a month.

Dark Chocolate Cake Layers

  • While the mousse chills, make the dark chocolate cake layers. Preheat oven to 350°F / 175°C and line and grease a 9x13-inch quarter sheet cake pan or 2, 9-inch cake pans with parchment paper and non-stick spray. If you have heating cores, place two heating cores in the 13x9 pan or one heating core in each 9-inch pan and generously spray them with non-stick spray. This helps the cake bake up more evenly and quickly. Set aside.
  • Mix 2 1/2 cups sugar, 2 1/4 cups all-purpose flour, 3/4 cup dark cocoa powder, 2 1/2 tsp baking powder, and 1 tsp salt together in a stand mixer with a paddle attachment or hand mixer until fully combined.
  • Mix 1 cup of room temperature, unsalted butter slowly into the dry ingredients at a low speed. Continue to mix until no large chunks of butter remain and the mixture looks like moist sand.
  • Pour in 1 cup of egg whites and mix on low until just incorporated. Mix in 1 1/2 cups of buttermilk in two installments on a low speed.
  • Add in 2 Tbsp of vegetable oil, 2 tsp of vanilla extract, and 1 tsp of instant espresso. Mix on a low speed until incorporated. Scrape down the sides of the bowl with a rubber spatula, then beat on a medium speed for about 30 seconds to make sure everything is properly mixed together.
  • Pour the batter into the prepared pan(s). Bake a 9x13-inch pan for 40-45 minutes (add 3-5 minutes if you aren't using heating cores), or bake 2, 9-inch cake pans for 34-37 minutes (add 2-3 minutes if you aren't using heating cores).
  • Let the pans cool for 10 minutes, then run a small offset spatula around the perimeter of the pan to separate the cake from the pan. Then place the pan(s) in the freezer for 30 minutes to speed up cooling. Once the layer(s) are fully cooled, carefully flip the pans and remove the layer(s).
  • Use a serrated knife to level the top of the layer(s). If you made a 9x13-inch cake, cut it in half to make 2, 9x6.5-inch pieces. Set aside.
  • Wrap and freeze the layers at this point if you're making them in advance. If you do make these cake layers in advance and freeze them, let them thaw for about 20 minutes before making this cake. The cake layers should still be slightly cold to the touch, which will make it easier to assemble the cake.

Chocolate Simple Syrup - Optional

  • This step is optional, but I love to soak the cake layers in chocolate simple syrup so the cake stays moist for several days, especially since the sides of the cake aren't covered. Pour 1/2 cup of water and 1/2 cup of granulated sugar into a small saucepan. Cook over medium heat, stirring occasionally until the mixture starts to boil.
  • Remove from heat and whisk in 1 Tbsp cocoa powder. Pour into a small bowl to cool to room temperature, then cover and set aside. If you're making this in advance, it can be stored in an airtight container in the fridge for up to 3 weeks. 

Assembling this Chocolate Tuxedo Mousse Cake

  • Now that all our components are ready for this tuxedo cake, it's time to assemble it! Spread a bit of chocolate ganache on a grease-proof cake board or flat plate to help keep the cake in place, then center the first cake layer on top of the ganache.
  • If you made the chocolate simple syrup, generously brush it over the cake layer using a silicone brush or a clean kitchen brush.
  • Cover the cake in an even layer of dark chocolate mousse, then top it with an even layer of white chocolate mousse.
  • Place the remaining cake layer on top of the mousse and soak the top of the layer with chocolate simple syrup. Use a small offset spatula or piece of acetate sheet to clean up the sides of the cake and give the mousse a sharp edge that's flush with the cake layers.
  • Chill the cake in the fridge for 15 minutes to help it keep its shape. Then spread the chocolate ganache in a thick layer on top of the cake with a small offset spatula.
  • Decorate the top of the cake with chocolate sprinkles and/or chocolate pearls, then enjoy! Serve cold for the cleanest slices, or for a less-chilled bite, let it sit at room temp up to 1 hour. Don’t leave it out longer than that or the mousse will soften/deflate.

Video

Notes

 
This recipe can also be used to make 3 8-inch cake layers with two layers of filling. Bake the layers at 350°F / 175°C for 33-35 minutes, or until a toothpick inserted in the center comes out with a few moist crumbs. 

My Tips for Making the Best Tuxedo Cake

  • When making the chocolate and white chocolate mousse, chill your mixing bowl and whisk attachment in the freezer. It makes it easier and quicker to whip up the whipped cream for the mousse.
  • Ingredients at room temperature mix together better! Set out any cold ingredients that need to be at room temperature ahead of time.
  • Properly measure your flour (spoon into the cup measure, then level). Or better yet, use a kitchen scale to measure your dry ingredients.
  • Level your room temperature or thawed cake layer(s) with a serrated knife to make them easier to stack.
  • Chill your cake layer(s) in the freezer for about 20 minutes before assembling the cake. It makes it so much easier to stack and frost them!

Making This Tuxedo Cake in Advance & Storage Tips

You can make these cake layers in advance and freeze them. It breaks the process up and makes it more approachable.
The white and dark chocolate mousse can also be made in advance! It can be made up to 2 days in advance and stored in the fridge.
You can also make the chocolate ganache frosting ahead of time or save any leftover frosting! It can be stored in an airtight container in the fridge for up to a month.
This cake can also be stored in the fridge for up to 3 days or in the freezer for up to a month. I recommend covering the cake with plastic wrap or placing it in an airtight container to keep it moist.

Nutrition

Serving: 1 | Calories: 466kcal | Carbohydrates: 52g | Protein: 6g | Fat: 27g | Saturated Fat: 15g | Polyunsaturated Fat: 10g | Cholesterol: 64mg | Sodium: 322mg | Fiber: 1g | Sugar: 40g