Blueberry Custard Cake with Swiss Buttercream
Recently, I made a decadent Blueberry Custard Cake for Karl’s birthday, and it was a hit! With layers of soft, buttery cake, rich blueberry compote, and creamy custard, all wrapped in a smooth Swiss buttercream, this cake is perfect for any special occasion. Trust me, it’s worth every bit of effort!
Equipment
- 3 Medium mixing bowls
- Saucepan
- 2 8” round baking pans
- 1 Electric mixer
- 1 Parchment paper
- 1 Baking strips (optional for even cakes)
- 1 Spatula
- 1 Whisk
- 1 Piping bag or Ziploc bag
Ingredients
For the Custard Filling:
- 4 egg yolks 3 tablespoons
- 1 whole egg
- 3 tablespoons cornstarch
- ½ cup sugar divided
- 2 cups milk
- ⅛ teaspoon salt
- 1 teaspoon vanilla extract
- 2 tablespoons unsalted butter
- ½ cup heavy cream
- 3 confectioner’s sugar
For the Blueberry Compote:
- 1 pint fresh blueberries (extra for decoration)
- ½ cup granulated sugar
For the Cake:
- ¾ cup buttermilk
- ½ teaspoon baking soda
- 1 cup unsalted butter softened
- 1½ cups sugar granulated
- 1 teaspoon vanilla extract pure
- 2 whole eggs
- ⅔ cup blueberry compote
- ¼ teaspoon salt
- 5 tablespoons cornstarch
- 2 cups all-purpose flour
- 3 tablespoons all-purpose flour
For the Swiss Buttercream:
- 6 large egg whites (or 170 grams liquid egg whites)
- 1¼ cups granulated sugar (250 grams)
- Pinch of salt
- 3 sticks unsalted butter softened but cool (340 grams)
- 4 tablespoons blueberry compote
Instructions
For the Custard Filling:
- Prepare the Custard: In a medium bowl, whisk together the egg yolks, whole egg, cornstarch, and ¼ cup sugar. Set aside.
- Heat the Milk: In a saucepan, heat the milk, remaining ¼ cup sugar, and salt over medium heat until just boiling. Remove from heat.
- Temper the Eggs: Slowly add ⅓ of the hot milk mixture to the egg mixture, whisking continuously to prevent curdling. Pour the tempered eggs back into the saucepan with the remaining milk.
- Cook the Custard: Return the saucepan to the stove and cook, stirring continuously, until the mixture thickens and boils. Cook for an additional 2 minutes, then remove from heat and stir in vanilla extract and butter.
- Chill: Cover the custard with cling wrap directly on the surface to prevent a skin from forming. Refrigerate for at least 2 hours until cold and firm.
- Whip the Cream: Whip the heavy cream and confectioner’s sugar until stiff peaks form. Fold the whipped cream into the chilled custard and refrigerate until ready to use.
For the Blueberry Compote:
- Cook the Blueberries: In a saucepan, combine blueberries and sugar. Cook over medium heat for about 10 minutes until thickened.
- Blend: Blend the compote until smooth and let it cool to room temperature.
For the Cake:
- Preheat Oven: Preheat the oven to 350°F (175°C). Grease and flour two 8” round baking pans, lining the bottoms with parchment paper.
- Mix Buttermilk: In a small bowl, mix the buttermilk with baking soda. Set aside.
- Cream Butter and Sugar: Using an electric mixer, cream the butter and sugar on medium speed for 3-4 minutes until light and fluffy. Add the vanilla and eggs, one at a time, mixing well after each addition.
- Add Compote: Stir in the buttermilk mixture and blueberry compote.
- Combine Dry Ingredients: In a separate bowl, whisk together salt, cornstarch, and flour. Gradually add to the wet ingredients, mixing until just combined.
- Bake: Divide the batter evenly between the two prepared pans. Bake for 34 minutes, or until a toothpick inserted in the center comes out clean. Let the cakes cool completely before frosting.
For the Swiss Buttercream:
- Heat Egg Whites: In a heatproof bowl (preferably your mixer bowl), whisk together the egg whites, sugar, and salt. Place the bowl over simmering water, whisking until the mixture reaches 160°F (71°C).
- Whip: Remove from heat and whip on medium-high speed until the mixture is fluffy and cooled to room temperature.
- Add Butter: Add the softened butter one stick at a time, whipping until the frosting is smooth and thick. Mix in the blueberry compote.
To Assemble:
- Layer the Cake: Place one cake layer on a serving plate. Pipe a thick ring of Swiss buttercream around the edge and fill the center with custard filling.
- Top and Frost: Place the second cake layer on top. Frost the entire cake with the remaining Swiss buttercream.
- Decorate: Decorate with fresh blueberries.
Video
Notes
Even Layers: Use baking strips to ensure your cake layers bake evenly.
Chill Before Assembling: Make sure the cakes, custard, and buttercream are all cool before assembling to prevent melting.
Storage: The cake can be stored in the refrigerator for up to 3 days. Bring to room temperature before serving.