Sourdough Chocolate Sheet Cake with Brown Butter Buttercream
This rich and moist sourdough chocolate sheet cake is topped with a nutty brown butter buttercream for a bakery-worthy finish. Made with simple ingredients and discard you might otherwise toss, it’s an easy, crowd-pleasing dessert you'll make again and again.
Equipment
- Kitchen scale (please weigh your ingredients)
- Stand mixer (or large mixing bowl with an electric mixer)
- medium bowl for mixing dry ingredients
- 9x13 baking pan
- Parchment Paper
- Flour sifter (optional)
- Piping bag (optional)
- Icing tip of choice (optional)
Ingredients
For the sourdough chocolate sheet cake
- 1 ⅕ cup all-purpose flour 180g
- 1 cup cocoa powder 80g
- 2 teaspoons baking powder
- 1 ½ teaspoons baking soda
- ½ teaspoon salt
- 4 eggs room temperature
- ⅔ cup sourdough discard 200g
- 1 cup cane sugar 200g
- 1 cup brown sugar packed 240g
- ⅔ cup vegetable oil 158ml
- 4 teaspoons vanilla extract
- 1 cup milk 236 ml
For the brown butter buttercream
- ¾ cup butter for the brown butter 142g (111g after browning)
- ½ cup butter softened, 113g
- 1 teaspoon vanilla
- 4.5 cups powdered sugar 450g
- 2 tablespoons milk
Instructions
Prep
- Preheat your oven to 350F and prepare a 9x13 pan with parchment paper or nonstick spray/butter.
- Brown your butter at least an hour or two before decorating and allow it to cool to room temperature before making the buttercream.
For the sourdough chocolate cake
- If you want to ferment your batter, see the notes below for the instructions you'll need a day in advance.
- In a large mixing bowl, mix your dry ingredients together. Set aside.1 ⅕ cup all-purpose flour, 1 cup cocoa powder, 2 teaspoons baking powder, 1 ½ teaspoons baking soda, ½ teaspoon salt
- In a medium bowl, mix together your wet ingredients. Slowly mix your wet ingredients into your bowl of dry ingredients until just combined. The batter will be thin; do not overmix and do not add the dry ingredients to the wet ingredients (this will lead to lumps of flour in the batter)!4 eggs, ⅔ cup sourdough discard, 1 cup cane sugar, 1 cup brown sugar, ⅔ cup vegetable oil, 4 teaspoons vanilla extract, 1 cup milk
- Pour the batter into your prepared 9x13 pan and bake the your cake for 30-35 minutes at 350F until a toothpick inserted in the center comes out clean. Allow to cool completely before decorating.
For the brown butter buttercream
- In the bowl of a stand mixer with a paddle attachment, cream the room temperature butter and brown butter until smooth and creamy. Add vanilla extract and mix until combined.¾ cup butter for the brown butter, ½ cup butter, 1 teaspoon vanilla
- Gradually add in your powdered sugar ½ a cup at a time to prevent the powder from flying out of the stand mixer when you turn it on.4.5 cups powdered sugar
- Add in milk 1 tablespoon at a time until you reach your desired consistency.2 tablespoons milk
- Smooth the buttercream over your cooled cake and top with chocolate shavings, berries, and/or sprinkles. Enjoy!
Notes
Long fermentation: Mix flour, milk, sourdough starter, and oil in a bowl. Cover and store in your fridge for 24 hours. Alternatively, you can leave it at room temperature overnight to ferment, as the bacteria in the starter will prevent the milk from spoiling. The next day, add the remaining ingredients and bake from there!
Salted butter in buttercream: I prefer salted butter in my buttercreams, but if you'd rather use unsalted, just add a pinch of salt to the buttercream. If using dairy free butter, don't add salt as they are usually well salted.
Storage: Store at in the refrigerator for up to 4 days in an airtight container.
Chocolate shavings: To make chocolate shavings/curls, run a potato peeler along a chocolate bar.