Description

This White Chocolate Mousse Cake combines delicate white chocolate mousse with moist, fluffy white cake layers and a rich white chocolate buttercream frosting. Perfect for special occasions, this elegant dessert features layers of whipped white chocolate mousse nestled between vanilla cake layers, all finished with luscious buttercream and decorative swirls. The cake is made from scratch using quality ingredients and can be prepared in advance, making it a show-stopping treat for celebrations.

Ingredients

Scale

White Chocolate Mousse

1 1/3 cups good quality white chocolate chips (215g)
1 1/2 cups heavy cream or heavy whipping cream, cold – divided (360ml)
1/4 cup powdered sugar (30g)
1 tsp vanilla extract or vanilla bean paste (4ml)
pinch fine salt (less than 1/8 tsp)

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 (56ml)
1 tsp vanilla extract or vanilla bean paste (4ml)

White Chocolate Buttercream Frosting

2 cups unsalted butter, room temperature (452g)
7 cups powdered sugar (900g)
1 tsp vanilla extract or vanilla bean paste (4ml)
1/2 tsp fine salt (3g)
1/3 cup heavy whipping cream, room temperature (75g)
1 cup white chocolate chips, melted and cooled (160g)

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Instructions

Prepare the White Chocolate Mousse: Combine white chocolate chips and 1/2 cup heavy cream in a microwave-safe bowl, heat for 60-75 seconds, then stir until smooth and melted. In a separate large bowl or stand mixer with whisk attachment, whip 1 cup heavy cream, powdered sugar, vanilla, and salt on medium-high speed until thick peaks form (about 2.5-3 minutes). Fold half the whipped cream gently into the white chocolate mixture, then fold in the rest carefully to maintain volume. Cover and chill the mousse for at least 2 hours.
Make the White Cake Layers: Preheat oven to 325°F (163°C). Grease and line four 7-inch cake pans or three 8-inch pans with parchment. Cream butter and granulated sugar in a stand mixer with whisk attachment on high until light and fluffy, scraping sides as needed. Add egg whites at medium speed until incorporated. In a separate bowl, whisk cake flour, baking powder, and salt. Add half the dry ingredients to the butter mixture on low, then add sour cream, oil, and vanilla, mixing just to combine. Add remaining dry ingredients at low speed. Divide batter evenly among pans and bake 37-40 minutes until a toothpick comes out with moist crumbs. Let cool 10 minutes, then loosen edges and freeze layers 45 minutes for easier handling. Level the tops and trim sides with a serrated knife.
Prepare the White Chocolate Buttercream Frosting: Beat butter on low speed until smooth. Mix in vanilla and salt. Gradually add powdered sugar intermixed with heavy cream to reach desired consistency. Stir in melted and cooled white chocolate on low speed, scraping bowl as needed, until fully incorporated and smooth. Adjust thickness by adding more cream or powdered sugar as necessary. Transfer to a piping bag, seal, and cut a 3/4 inch opening at the base.
Assemble the Cake: Place the first cake layer on a greaseproof cake board, attaching with a dab of frosting. Pipe a buttercream ring around the edge. Spread an even layer of white chocolate mousse inside the ring (about one-third mousse per layer if using four layers). Repeat for remaining layers. Apply a thin crumb coat with frosting around cake, smooth with bench scraper, and chill 30 minutes (or 10 minutes in freezer). Add a second thicker frosting coat and smooth with an icing comb. Pipe decorative buttercream swirls with a Wilton 1M tip and garnish with sprinkles if desired.

Notes

Chill mixing bowl and whisk attachment before whipping cream for better volume.
Properly measure flour by spooning and leveling or use a kitchen scale for accuracy.
Do not overmix cake batter to keep layers tender and fluffy.
Use a kitchen scale to weigh cake pans for even layers.
Tap pans on the counter before baking to remove air bubbles.
Level cake layers at room temperature or after thawing for easy stacking.
Freeze leveled cake layers about 20 minutes before assembling for stability.
Make cake layers and mousse ahead and store properly to save time on the day of serving.
Buttercream frosting can be stored up to one month in the fridge or three months in the freezer; stir well before use.
Frosted cake keeps well refrigerated up to one week or frozen for one month.
Cover leftover cut cake sections with frosting to maintain moisture.

Nutrition

Serving Size: 1 slice (approximate, based on 24 slices)
Calories: 430 kcal
Sugar: 35 g
Sodium: 110 mg
Fat: 28 g
Saturated Fat: 17 g
Unsaturated Fat: 9 g
Trans Fat: 0.5 g
Carbohydrates: 40 g
Fiber: 0.5 g
Protein: 4 g
Cholesterol: 80 mg