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image of a slice of strawberry mousse cake that's been cut into to show how delicious it is
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4.91 from 11 rating

Strawberry Mousse Cake

This strawberry mousse layer cake recipe is made with fluffy white cake layers, the fluffiest strawberry mousse filling, and strawberry buttercream frosting.
Prep Time15 minutes
Cook Time45 minutes
Additional Time2 hours
Total Time3 hours
Course: Cakes
Cuisine: American
Servings: 24
Calories: 628kcal
Author: Chelsey White

Ingredients

Strawberry Mousse

  • 1 cup good quality white chocolate chips 180g
  • 1 1/3 cups heavy cream or heavy whipping cream, cold - divided 320g
  • 1/2 cup freeze dried strawberry powder 56g
  • 1/4 cup powdered sugar 30g
  • 1 tsp vanilla extract or vanilla bean paste 4g
  • pinch fine salt less than 1/8 tsp
  • red gel food coloring - optional

White Cake Recipe

  • 1 cup (2 sticks) unsalted butter, room temperature 226g
  • 3 cups granulated sugar 600g
  • 1 cup carton egg whites or 7 large egg whites, room temperature 235g
  • 3 cups cake flour 360g
  • 2 1/2 tsp baking powder 10g
  • 1 tsp fine salt 6g
  • 1 1/2 cups full-fat sour cream, room temperature 380g
  • 1/4 cup vegetable or canola oil 56 ml
  • 1 tsp vanilla extract or vanilla bean paste 4ml

Strawberry Buttercream Frosting

  • 1 1/2 cups unsalted butter, room temperature 339g
  • 1/2 cup freeze dried strawberry powder 56g
  • 1 tsp vanilla extract or vanilla bean paste 4ml
  • 1/2 tsp fine salt 3g
  • 5 cups powdered sugar 625g
  • 1/4 cup strawberry jam 80g
  • 1 Tbsp lemon juice 12g

Additional Filling

  • 1/2 cup strawberry jam 160g

Tools and Equipment Needed

Instructions

Strawberry Mousse Cake Filling

  • Make the strawberry 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.
  • Add 1 cup white chocolate chips and 1/3 cup heavy cream in a medium-sized, heat-proof bowl. Heat for 45-60 second 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. If you don't have a microwave, you can also use a double boiler. Set aside.
  • Add 1 cup of heavy cream, 1/2 cup freeze dried strawberry powder, 1/4 cup powdered sugar, 1 tsp vanilla extract, and a pinch of fine salt into a large bowl or the bowl of a stand mixer fit with a whisk attachment. If desired, add a small drop of red gel food coloring to give this mousse a more vibrant color.
  • Mix on a medium-high speed until the whipped cream starts to gather in the whisk attachment and you can see texture around the edge of the bowl. The whipped cream should be thick and able to keep its shape. This usually takes about a minute or two in my stand mixer.
  • Gently fold half of the strawberry whipped cream into the white chocolate mixture using a rubber spatula. Use the spatula to swoop around the sides of the bowl and pull through the center like I show in the video of this recipe. Fold in the remaining strawberry whipped cream. Be careful not to over-mix the mousse, or it will become deflated and lose its structure.
  • Cover the mousse with plastic wrap and chill in the refrigerator for at least 2 hours. Make sure you keep the mousse chilled until right before you fill the cake because it can also lose its shape if it gets warm.

White Cake Layers

  • Preheat oven to 325°F / 162°C. Line and grease three, 8-inch cake pans with parchment rounds.
  • Add 1 cup of unsalted butter and 3 cups of granulated sugar into the bowl of a stand mixer. Mix together on a high speed with a whisk attachment for 3 minutes. Scrape down the sides of the bowl as needed with a rubber spatula. The mixture should become lighter in color as air is whipped into it.
  • Add in 1 cup of room temperature egg whites and mix at a medium speed until they're incorporated.
  • Whisk 3 cups of cake flour, 2 1/2 tsp baking powder, and 1 tsp salt together in a separate bowl.
  • Add half of the dry ingredients into the butter/egg mixture and mix on a low speed until incorporated.
  • Add in 1 1/2 cups sour cream, 1/4 cup oil, and 1 tsp vanilla extract and mix at a low speed until combined. Scrape the sides and bottom of the bowl as needed.
  • Mix in the remaining dry ingredients on a low speed.
  • Divide the batter evenly between the prepared cake pans. I like to use a digital kitchen scale to weigh my pans to make sure my layers bake up to be the same height.
  • Bake for 45-50 minutes, or until a toothpick comes out with a few moist crumbs. Rotate the pans halfway through to help them bake evenly. I know this seems like a long time, but it takes a bit longer than normal because we're baking these at 325°F / 162°C.
  • Let the pans cool for 10 minutes, then run an offset spatula around the perimeter of the pan to separate the cake from the pan.
  • Place the cake layers into the freezer for 45 minutes to accelerate the cooling process. Once the layers are fully cooled, carefully flip the pans and remove the layers from the pans.
  • Use a serrated knife to level the top of each cake layer.

Strawberry Buttercream Frosting

  • While the cake layers bake and cool, make the strawberry buttercream frosting.
  • Beat 1 1/2 cups butter on a low speed for 30 seconds with a paddle or whisk attachment until smooth.
  • Add in 1/2 cup freeze dried strawberry powder, 1 tsp vanilla extract, and 1/2 tsp salt and beat on a low speed.
  • Gradually mix in 5 cups of powdered sugar on a low speed. Add in 1/4 cup of strawberry jam and 1 Tbsp of lemon juice halfway through to make the frosting easier to mix.
  • Continue to mix until the ingredients are fully incorporated, and the desired consistency is reached. 
  • If the frosting seems too thick, add in additional cream (1 teaspoon at a time). If the frosting is too thin, add in more powdered sugar (quarter of a cup at a time).
  • Stir by hand with a rubber spatula to make the frosting extra smooth, then place the frosting in a large piping bag. Seal the top of the bag with a rubber band or clip and cut an opening that's about 3/4-inch wide at the base of the bag. Set aside.

Assembling This Strawberry Mousse Cake

  • Stack and frost the cake layers on a greaseproof cake board using a dab of frosting to help stick the first cake layer to the board.
  • Pipe a ring of strawberry buttercream around the perimeter of the cake layer. Spread 1/4 cup of strawberry jam inside the frosting ring, then top it with an even layer of strawberry mousse. Use about 1/2 of the mousse between each layer.
  • Repeat with the next cake layer. Once all the cake layers are stacked, spread a thin coat of frosting around the cake to fully cover the cake layers. If your layers are sliding around, insert a chopstick or wooden dowel into the center of the cake to make it more stable.
  • Smooth using a bench scraper, then chill the cake in the fridge (30 minutes) or freezer (10 minutes) until the frosting is firm to the touch.
  • Add a second, thicker layer of strawberry buttercream to the cake and smooth using a bench scraper.
  • Then decorate as desired! I chose to add some buttercream swirls and small strawberries in a semi-circle on top of the cake.

Video

Notes

Tips for Making the Best Strawberry Mousse Cake

  • When making the strawberry 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.
  • Properly measure your flour (spoon into the cup measure, then level). Or better yet, use a kitchen scale to measure your dry ingredients.
  • Mix your cake batter just until the ingredients are incorporated after adding in the flour. This ensures your cake layers are tender and fluffy.
  • Use a scale to weigh your cake pans as you fill them. This will make your cake layers bake to the same height and bake more evenly.
  • Bang your cake pans on the counter before putting them in the oven. This brings any air bubbles that are trapped in the batter to the surface.
  • Level your room temperature or thawed cake layers with a serrated knife to make them easier to stack.
  • Chill the leveled cake layers in the freezer for about 20 minutes before assembling the cake. It makes it so much easier to frost them!

Making This Strawberry Mousse Cake in Advance and Storage Tips

  • Make your cake layers in advance and freeze them. It breaks the process up and makes it more approachable.
  • Make your frosting ahead of time too or save any leftover frosting! It can be stored in an airtight container in the fridge for up to a month, or in the freezer for up to 3 months. Be sure to give it a good stir once it thaws to get the consistency nice and smooth again.
  • The strawberry mousse filling in this cake can be made up to two days in advance if stored in an airtight container in the fridge.
  • A frosted cake can last in the fridge for up to 2 days.

Nutrition

Serving: 1 | Calories: 628kcal | Carbohydrates: 80g | Protein: 5g | Fat: 33g | Saturated Fat: 18g | Polyunsaturated Fat: 12g | Cholesterol: 81mg | Sodium: 271mg | Fiber: 1g | Sugar: 62g