Strawberry Mousse Cake

Ingredients

• 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
• 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)
• 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)
• 1/2 cup strawberry jam (160g)
• Stand mixer or electric hand mixer
• Whisk attachment
• Greaseproof Cake Board
• Spinning Cake Stand
• Large Offset Spatula
• Bench Scraper

Instructions

1. 1

   --- Strawberry Mousse Cake Filling ---

2. 2

   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.

3. 3

   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.

4. 4

   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.

5. 5

   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.

6. 6

   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.

7. 7

   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.

8. 8

   --- White Cake Layers ---

9. 9

   Preheat oven to 325°F / 162°C. Line and grease three, 8-inch cake pans with parchment rounds.

10. 10

    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.

11. 11

    Add in 1 cup of room temperature egg whites and mix at a medium speed until they're incorporated.

12. 12

    Whisk 3 cups of cake flour, 2 1/2 tsp baking powder, and 1 tsp salt together in a separate bowl.

13. 13

    Add half of the dry ingredients into the butter/egg mixture and mix on a low speed until incorporated.

14. 14

    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.

15. 15

    Mix in the remaining dry ingredients on a low speed.

16. 16

    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.

17. 17

    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.

18. 18

    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.

19. 19

    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.

20. 20

    Use a serrated knife to level the top of each cake layer.

21. 21

    --- Strawberry Buttercream Frosting ---

22. 22

    While the cake layers bake and cool, make the strawberry buttercream frosting.

23. 23

    Beat 1 1/2 cups butter on a low speed for 30 seconds with a paddle or whisk attachment until smooth.

24. 24

    Add in 1/2 cup freeze dried strawberry powder, 1 tsp vanilla extract, and 1/2 tsp salt and beat on a low speed.

25. 25

    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.

26. 26

    Continue to mix until the ingredients are fully incorporated, and the desired consistency is reached.

27. 27

    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).

28. 28

    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.

29. 29

    --- Assembling This Strawberry Mousse Cake ---

30. 30

    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.

31. 31

    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.

32. 32

    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.

33. 33

    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.

34. 34

    Add a second, thicker layer of strawberry buttercream to the cake and smooth using a bench scraper.

35. 35

    Then decorate as desired! I chose to add some buttercream swirls and small strawberries in a semi-circle on top of the cake.