It’s Chloe and Leo’s birthday month, which means I’m fully in cake mode—testing, tweaking, and dreaming up something celebratory. (Chloe has already requested strawberry olive oil with verbena buttercream; Leo has his heart set on red velvet.) When it comes to birthdays, I always come back to a classic, with a little spin.
This one is a simple vanilla cake, light and fluffy, subtly elevated with sourdough discard and filled with warm vanilla flavor. It’s finished with a boysenberry buttercream—lush, berry-stained, and unmistakably summery. The color alone feels like celebration, deep and joyful, and the flavor is pure nostalgia: sweet, tart, and playful in the very best way.
Baker’s Notes
• This vanilla cake is best enjoyed the day it’s made.
• If you prefer to skip the sourdough discard, increase the flour to 190 grams.
• A lemon cake would also be lovely paired with the boysenberry buttercream.
• I wait all year for boysenberries at the farmers market. Marionberries, blackberries, or raspberries are all beautiful swaps, and frozen berries work well too.
Sourdough Vanilla Cake with Boysenberry Buttercream
Ingredients
Sourdough Vanilla Cake- adapted from Odette Williams
1¼ cups (165 g) all-purpose flour
½ cup (120 ml) whole milk or buttermilk
2 large eggs, at room temperature
¾ cup (150 g) granulated sugar
1 teaspoon baking powder
¼ teaspoon baking soda
¼ teaspoon salt
¼ cup (50 g) sourdough discard
½ cup (115 g) unsalted butter, at room temperature
1 tablespoon vanilla extract
3 tablespoons avocado oil
Boysenberry Buttercream
1 cup (120 g) boysenberries
3½ cups (500 g) powdered sugar, sifted
2 tablespoons (30 ml) heavy cream
¾ cup + 2 tablespoons (190 g) unsalted butter, at room temperature
½ teaspoon lemon juice
½ teaspoon kirsch (optional)
Instructions
Sourdough Vanilla Cake
- Preheat the oven to 350 F. Grease and one 8” in cake pans or 8 mini loaf pans.
- Place a large sifter over a bowl and add the flour, baking powder, baking soda and salt and sift.
- In the bowl of a stand mixer fitted with the paddle attachment, beat the butter for 30 seconds. Add the sugar and continue beating on medium speed until light and fluffy, about 4 minutes.
- Add the vanilla and sourdough discard and mix to combine.Gradually add the eggs.
- On low speed add the flour and then the oil and milk. Mix until just combined- don’t over mix.
- Transfer the batter to the prepared pans. Bake for 25-30 minutes for mini loaves, and 40-50 minutes for cake pan.
- Allow to cool for 10 minutes before transferring to a cooling rack to cool completely.
Boysenberry Buttercream
- Puree the berries with 2 tablespoons of powdered sugar until smooth, then strained through a fine mesh strainer to remove the seeds.
- Transfer the puree to the bowl of a stand mixer fitted with the paddle attachment. Add the cream, butter and 1 3/4 cups (250g) of powdered sugar and beat on low speed for 3 minutes. Add the rest of the powdered and beat for another 3 minutes, until creamy.
- Add the lemon juice and kirsch and mix until combined.
- Frost and decorate with berries and blooms!
Notes
To make the vanilla cake without sourdough, increase the flour to 190 grams.
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