This Sourdough Chocolate Sheet Cake is rich, moist, and deeply chocolatey with just the right touch of tang from sourdough discard. It’s topped with a luscious brown butter buttercream that’s nutty, silky, and totally unforgettable.
The sourdough cake has that soft, tender crumb you want in a classic chocolate cake—only better, thanks to the discard’s subtle depth. It's simple enough for a weeknight bake, but delicious enough for a celebration.
I made this cake for my youngest's first birthday, and it was a hit; my brother said it tastes a bit like a hot fudge sundae pop tart, which is a win in my book!
This cake is a perfect fit for birthdays, potlucks, or casual get-togethers when you want something that feels both nostalgic and a little elevated. It also shines during fall and winter months, when cozy flavors like brown butter feel extra special.
Serve it for Valentine’s Day, family dinners, or anytime you’re craving an easy dessert that still impresses. It travels well, serves a crowd, and is the kind of bake people ask you for the recipe after tasting.
If you love this cake, be sure to try my Sourdough Chocolate Cupcakes, which inspired this recipe. You’ll also adore my Sourdough Discard Brown Butter Chocolate Chip Cookies—they’re chewy, cozy, and just as rich in flavor.
Ingredients
You’ll only need basic pantry staples, plus sourdough discard and butter—most of which you likely already have on hand.
FOR THE SOURDOUGH CHOCOLATE CUPCAKES:
- All purpose flour
- Cocoa powder
- Baking soda
- Baking powder
- Salt
- Large eggs
- Sourdough discard (active sourdough starter works too)
- Oil (vegetable oil or coconut oil)
- Milk
- Vanilla extract
- Sugar
- Brown sugar
FOR THE CHOCOLATE FROSTING (NOT PICTURED IN THE ABOVE INGREDIENT PHOTO):
- Butter (Salted or unsalted butter works fine)
- Powdered sugar
- Vanilla extract
- Milk
- Sprinkles (I like these dye-free ones)
See recipe card for quantities.
Instructions
The recipe comes together in just a few easy steps, with no fancy tools or techniques required. You'll find step-by-step instructions with pictures below, as well as more in-depth directions in the recipe card at the bottom of this post.
Step 1: The night before, (or at least 2 hours before you need the buttercream) brown your butter on medium low heat, stirring regularly to prevent burning. You will start with 142g and end with 111g.
Step 2: When the brown butter is finished, it will be nice and golden brown with brown flecks at the bottom.
Let the butter cool at room temperature until it is solid and cool before using it in the buttercream.
Step 2: Preheat your oven to 350°F and prepare your muffin tin with cupcake liners.
Mix the wet and dry ingredients separately.
In a large mixing bowl or bowl of a stand mixer with a paddle attachment, slowly add the wet ingredients into the dry ingredients, stirring carefully so as not to overmix the batter. (Overmixing can cause sinking or overly dense cupcakes.)
Step 3: Pour the batter into a prepared 9x13 pan. I like to line mine with parchment paper (I cut tabs into the sides so that the parchment paper fits into the pan perfectly.
Bake your sourdough chocolate cake for 30-35 minutes at 350°F. It will be done when the top is set and a toothpick inserted in the center comes out clean.
Step 4: Once the cake is cool, add the softened butter and brown butter to the bowl of a stand mixer or large mixing bowl and whip at medium low speed with a paddle attachment until light and fluffy.
Step 5: Add the powdered sugar in gradually (small incraments are necessary to prevent the powdered sugar from flying out of the bowl once you turn the mixer on).
Add the milk in 1 tablespoon at a time until you reach your desired spreadable consistency.
Whip it with the paddle attachment for 5-8 minutes until the icing is perfectly smooth and light.
Spread the icing generously onto your cooled cake and decorate however you'd like.
Hint: Use a flour sifter to add the powdered sugar to the buttercream to ensure a smooth, easy-to-pipe frosting if piping is something you want to do.
Substitutions
If some of the ingredients don't work for you, that's totally fine!! Here are some of my recommended substitution ingredients.
- Milk: Use high-fat non-dairy milk if you don't want to use dairy! I highly recommend Oatly oat milk (full-fat or regular would be ideal).
- Butter: Use a non-dairy butter like Country Crock's plant butter. I've also had great luck using that brand in frosting.
Variations
This recipe can be easily switched up to create new and interesting flavors. Here are some fun ideas to try out!
- Espresso: Add 2 teaspoons of instant espresso powder with your flour or with the powdered sugar in the buttercream.
- Toppings: Top with berries, oranges, chocolate curls, sprinkles, or Oreo cookie crumbles. For holidays, use festive sprinkles!
- Buttercream: You can swap this recipe for vanilla buttercream or try something a bit more fun like the strawberry buttercream frosting in my strawberry crunch cupcake recipe. You can make it without the "crunch" if you'd prefer!
- Long-fermented: 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!
- Double chocolate: Add 1.5 cups of chocolate chips to the cake batter before baking. The same amount of walnuts would be delicious too!
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)
Storage
Store in an airtight container in the refrigerator for up to 4 days.
Can be frozen for up to 6 months, covered in plastic wrap and aluminum foil. Flash freeze it uncovered first, then wrap in plastic wrap, followed by aluminum foil. Thaw it in the fridge to keep condensation from ruining the frosting.
Top tip
Weigh your ingredients! I can't recommend this enough. Kitchen scales are easy to find, affordable, and beneficial to your baking journey. It is the best way to make sure your recipes turn out as accurate as possible. See my "equipment" section above for links to scales I recommend.
FAQ
Absolutely! Check out my "substitutions" section above for my favorite dairy alternatives for baking.
Related
Looking for other recipes like this? Try these:
Sourdough Chocolate Sheet Cake with Brown Butter Buttercream
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!
Comments
No Comments