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Moist and fluffy layers of chai-spiced cake between layers of creamy white chocolate mousse and frosted with the silkiest brown sugar buttercream!

Chai Spice Cake with Whipped Brown Sugar Buttercream

Moist and fluffy layers of chai-spiced cake between layers of creamy white chocolate mousse and frosted with the silkiest brown sugar buttercream!
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Prep Time 1 hour 30 minutes
Cook Time 18 minutes
Chilling Time 1 hour 30 minutes
Total Time 3 hours 18 minutes
Course Dessert
Cuisine American
Servings 10 Servings

Ingredients
  

Cake:

  • 1 Chai tea bag
  • ½ cup boiling water
  • 1 ¾ cup all-purpose flour
  • 1 teaspoon baking powder
  • ½ teaspoon baking soda
  • ½ teaspoon salt
  • 1 teaspoon ground cinnamon
  • ¼ teaspoon ground cardamom
  • ¼ teaspoon ground allspice
  • ¼ teaspoon ground ginger
  • ¼ teaspoon ground nutmeg
  • ⅛ teaspoon ground cloves
  • ¾ cup unsalted butter, softened
  • 1 cup granulated sugar
  • 2 eggs
  • ¾ cup sour cream
  • 1 teaspoon vanilla

White Chocolate Mousse:

  • 8 ounces white chocolate, chips or chopped
  • 1 ½ cup heavy cream, divided

Whipped Brown Sugar Buttercream:

  • 7 Tablespoons all-purpose flour
  • 1 ⅓ cup milk
  • 1 ¼ cup unsalted butter at room temperature
  • 1 ½ cup brown sugar
  • 2 teaspoons vanilla
  • ¼ teaspoon salt

Instructions
 

Make the Cake:

  • Place tea bag in a cup or bowl and pour the boiling water over it; steep for 15 minutes. Allow to cool.
  • Preheat the oven to 350ºF degrees. Line three 8-inch round cake pans with parchment paper and spray with nonstick cooking spray.
  • In a mixing bowl, whisk the flour, baking powder, baking soda, salt and spices together 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 eggs, one at a time, until combined, scraping down the sides and bottom of the bowl as needed. Beat in the sour cream and vanilla on medium speed.
  • Pour the dry ingredients into the wet ingredients and mix until combined. Add the chai water, then mix until just combined, scraping down the sides and bottom of the bowl as needed.
  • Divide batter among the three pans, spreading it out into an even layer. Bake for 15-18 minutes or until a toothpick inserted in the center comes out clean. Allow to cool in the pan for 10 minutes before transferring to a wire rack to cool completely.

Make the Mousse:

  • Place chocolate in a medium microwave-safe bowl. Add 3 Tablespoons of the heavy cream. Heat in the microwave for 30-45 seconds, remove and stir until smooth. Allow to cool to room temperature.
  • Place the remaining heavy cream in a well-chilled bowl of a stand mixer fitted with the whisk attachment. Whip on high until stiff peaks form.
  • Stir a quarter of the whipped cream into the melted chocolate until smooth and completely incorporated. Add the combined whipped cream and chocolate mixture to the remaining whipped cream and use a rubber spatula to gently fold together. Refrigerate until ready to assemble cake.

Make the Buttercream:

  • In a small saucepan over medium heat, whisk flour and milk together, stirring constantly, until it thickens. It should look like thick pancake batter. Remove from heat and immediately pour milk mixture into a bowl to cool completely.*
  • After the milk mixture has come to room temperature, use a stand mixer fitted with the whisk attachment or a beater to cream the butter, sugar, vanilla, and salt together on medium high until light and fluffy, about 3 minutes.
  • Add the completely cooled milk mixture, and beat it for about 5-7 minutes on high until it looks like whipped cream.**

To Assemble:

  • Place a cake layer on a cake plate or pedestal. Pipe a border of buttercream along the perimeter of the cake to prevent filling from peeking out of the sides. Spread a third of the mousse on top and inside the frosting border. Repeat steps with the remaining cake layers and mousse, ending with a layer of mousse on top. Chill cake in the freezer for 1 hour.
  • Once chilled and solid, frost the cake with the buttercream.*** Freeze cake for at least 30 minutes to set the buttercream. Remove cake and frost with a final layer of buttercream. Decorate with sprinkles, if desired.

Notes

*The milk mixture can be refrigerated to speed up the cooling process.
**If your frosting still looks curdled after several minutes of beating, no need to panic! This is most likely because your butter or flour mixture was too cold. Simply remove a couple of tablespoons of the curdled mixture and place it into a small microwaveable bowl. Heat it in the microwave until it’s completely melted, then add it back into the mixing bowl. Turn the mixer on, and beat everything until it’s smooth. If it still looks curdled, just keep repeating this reheating technique a tablespoon at a time until the mixture comes together. Trust me, it eventually will!
***Since the filling will soften quicker than the cake layers, I recommend frosting the top first and then frosting the sides.