Both elegant and heavenly, this Blackberry White Chocolate Mousse Cake features moist and tender vanilla cake, blackberry white chocolate mousse, and luscious blackberry topping!
Ladies and gents, do I have a dazzler of a dessert for you!
With blackberry season just beginning here in the Pacific Northwest, I figured it was time to create a dessert that celebrates these sweet and slightly tart gems of nature. And what better way to honor them than with this stunning Blackberry White Chocolate Mousse Cake!
Why You’ll Love This Blackberry Beauty
Moist and Tender Cake: Infused with pure vanilla, fresh lemon, and sweet almond extract, this cake is absolute perfection for the tastebuds. It’s supremely moist and buttery, and it pairs so incredibly well with the mousse and blackberry topping.
Blackberry + White Chocolate Mousse: This light and airy mousse combines the tart sweetness of blackberries with the creamy vanilla sweetness of white chocolate. It’s smooth, creamy, and melts in your mouth.
Fresh Blackberry Topping: Made with plump juicy blackberries, this delectable topping is bursting with fresh blackberry sweetness. Bright and bold in both flavor and color, this gorgeous blackberry topping adds an exquisite finish to the cake.
The Perfect Make-Ahead Dessert: Since the layers need time to set up, it’s best to make this cake the day before you plan to serve it. On the day of, all you have to do is un-mold it and garnish with some whipped cream and fresh berries.
Mousse Making Tips
Add STRAINED Blackberry Topping – To infuse the mousse with blackberry flavor, some of the fresh blackberry topping is added to it. However, before it’s added, it needs to be strained through a fine mesh sieve to remove any seeds or solids. While the seeds are perfectly fine in the top layer, you don’t want any in that smooth and creamy mousse.
Don’t Rush the Gelatin Process – To create that perfectly silky smooth and stable mousse, it’s important to follow the gelatin steps properly. This means blooming the gelatin in cold water (never hot water), letting it sit for a few minutes to soften and hydrate, then gently melting/dissolving the gelatin in the microwave for a few seconds. Never boil the gelatin, as overheating it will eliminate the gelatin’s setting power.
Temperature Matters – It’s important that your white chocolate base is still warm (not hot) when incorporating the warm gelatin mixture. If the base is too cold, the gelatin will seize and form lumps. I recommend using one hand to pour the gelatin mixture in a thin stream into the white chocolate base while using the other hand to whisk. Try to avoid hitting the whisk, or the gelatin will cling to it and harden.
Cool Before Folding – After the gelatin mixture has been incorporated into the white chocolate base, the mixture will still be quite warm at this point. Allow it to cool to room temperature before folding in the whipped cream so that you don’t deflate the mousse.
Gradually Fold in Whipped Cream – Once the white chocolate mixture has cooled to room temperature, lighten up the mixture by using a rubber spatula to fold in one cup of the whipped cream. Next, fold in the strained blackberry topping until mostly combined. You should still see streaks of purple throughout. Finally, add the rest of the whipped cream, gently folding everything together until just combined.
Assembly and Layering Tips
Use the Right Cake Pan – You can either bake this cake in a 9-inch springform pan or a regular 9-inch round cake pan. If using a regular cake pan, make sure to line it with parchment paper for easy removal. To achieve those pristinely smooth sides, I wrapped an adjustable cake ring (like this one) around the cake and lined it with acetate before adding the mousse on top. If you don’t have an adjustable cake ring, I would use a cake pan with tall removable sides, like a springform pan. If you don’t have acetate, you can also use parchment paper. The sides won’t be quite as smooth, but it’ll keep the layers intact. If you take this route, check out my Lemon Strawberry Mousse Cake for more instructions.
Cool the Cake Completely – The cake needs to be completely cool before the mousse is layered on top. If it’s too warm, the mousse will melt and your perfectly fluffy mousse will deflate into a goopy mess. If you must speed up the cooling process, chill the cake in the refrigerator after it’s been flipped out onto a wire rack.
Don’t Rush the Chill Time – Once the cake is fully assembled, you need to allow plenty of time for it to set up. I recommend a minimum of 4 hours in the refrigerator, but if you can give the cake an overnight chill, that’s even better.
Blackberry White Chocolate Mousse Cake
Ingredients
Cake:
- ¾ cup + 2 Tablespoons all-purpose flour
- ½ teaspoon baking powder
- ¼ teaspoon baking soda
- ⅛ teaspoon salt
- 6 Tablespoons unsalted butter, softened
- ½ cup granulated sugar
- 1 egg
- ⅓ cup sour cream
- 1 teaspoon vanilla
- ⅛ teaspoon almond extract
- 1 Tablespoon lemon juice
- 1 Tablespoon lemon zest
- ¼ cup milk
Blackberry Topping:
- 4 cups blackberries (fresh or frozen)
- ⅔ cup granulated sugar
- 3 Tablespoons cornstarch
- ⅛ teaspoon of salt
- 2 teaspoons lemon juice
Blackberry White Chocolate Mousse:
- ½ cup blackberry topping (from recipe above)
- 3 cups heavy cream, divided
- 12 ounces white chocolate, chips or chopped
- 4 teaspoons unflavored gelatin
- 3 Tablespoons cold water
To Decorate:
- Freshly-whipped cream
- Fresh blackberries
- White chocolate curls*
Instructions
Make the Cake:
- Preheat oven to 350ºF. Line a 9-inch round cake pan with parchment paper and spray with nonstick cooking spray.
- In a mixing bowl, whisk together the flour, baking powder, baking soda, and salt until combined; set aside.
- In the bowl of a stand mixer fitted with a paddle attachment, beat the butter and sugar together on medium speed until lightened and creamy. Beat in the egg until combined, scraping down the sides and bottom of the bowl as needed. Beat in the sour cream, vanilla, almond extract, lemon juice, and zest on medium speed.
- Pour the dry ingredients into the wet ingredients and mix until combined. Add the milk and mix until just combined, scraping down the sides and bottom of the bowl as needed.
- Pour batter into prepared pan, smoothing out evenly. Bake for 18-22 minutes, or until a toothpick inserted in the center comes out clean. Allow to cool completely before flipping out of the pan and onto a wire rack.
- Once completely cool, wrap a sheet of acetate (or parchment paper) about 6 inches tall around the edges of the cake to create a "wall". Secure the cake in a cake ring or springform pan that's at least 6 inches tall.
Make the Blackberry Topping:
- In a medium saucepan, heat the blackberries over medium heat until they soften and their juices start to release, about 3-4 minutes. In a separate bowl, combine the sugar, cornstarch, and salt. Add mixture to the blackberries and continue cooking until it begins to thicken, about 2-3 minutes. Pour into a shallow bowl and stir in the lemon juice. Place in the refrigerator to cool completely.
Make the Mousse:
- Place a fine mesh sieve over a bowl. Pour 1/2 cup blackberry topping into the sieve, straining out the seeds and solids. Set strained berry sauce aside.
- In the chilled bowl of a stand mixer fitted with a whisk attachment, beat 2 cups of the heavy cream until stiff peaks form. Set aside in the refrigerator.
- Place white chocolate into a medium bowl. Pour 1 cup of the heavy cream into a saucepan and heat until it begins to simmer. Immediately pour hot cream over the white chocolate and cover with plastic wrap. Let sit for 5 minutes. Remove plastic wrap and stir until completely smooth.
- In a small bowl, sprinkle the gelatin over the water; let stand 1 minute. Heat in the microwave for 10-15 seconds until gelatin is completely dissolved and liquified. Stir gelatin liquid into white chocolate mixture; allow to cool slightly.
- Fold 1 cup of the whipped cream into the white chocolate mixture to lighten it up. Then fold in the strained berry sauce until mostly combined. Add the rest of the whipped cream, folding until just combined. Spread mousse evenly over the cake. Chill in the freezer for about 15-20 minutes.
- Spread the blackberry topping evenly over mousse layer. Chill cake in the refrigerator until set, about 4 hours. I recommend an overnight chill.
Decorate the Cake:
- Once cake is completely set and firm, remove the cake ring (or springform pan) and the acetate (or parchment paper). Carefully transfer cake to a platter. Decorate with freshly-whipped cream, fresh blackberries and white chocolate curls.
Notes