My Sourdough Chocolate Sheet Cake with Brown Butter Buttercream is rich, deeply chocolatey, and tender with just the right touch of tang from sourdough discard — topped with a nutty, silky brown butter buttercream that makes the whole thing taste like a bakery-worthy celebration cake. My brother described it as tasting like a hot fudge sundae pop tart, and honestly, that's the best review I've ever gotten.
If you love a one-pan chocolate cake, my chocolate sheet cake with chocolate cream cheese frosting is the sister recipe — same format, totally different frosting situation. And if sourdough discard baking is your thing, my sourdough funfetti layer cake, my fudgy sourdough discard brownies or my sourdough lemon snack cake are always a good next stop.
Quick Look: Sourdough Chocolate Sheet Cake
⏱️ Ready In: About 3 hours (including brown butter chill time)
🔥 Bake Time: 30–35 minutes
🍽️ Serves: 15 people
✨ Calories: 568 per slice
🥄 Main Ingredients: Sourdough discard, cocoa powder, brown butter, powdered sugar
🌿 Dietary Info: Vegetarian
🍫 Why You'll Love It: A moist, tender chocolate cake made with discard you'd otherwise toss, topped with a brown butter buttercream that's nutty, fluffy, and completely unforgettable.
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Why You'll Love This Recipe
- It uses sourdough discard. Instead of tossing it, you're folding it into a chocolate cake batter where it adds subtle tang, moisture, and depth that a standard chocolate cake just doesn't have. Same discard-first philosophy behind my sourdough discard blueberry muffins and chewy brown butter sourdough chocolate chip cookies.
- Brown butter buttercream changes everything. Regular buttercream is fine. Brown butter buttercream is nutty, slightly caramelized, and makes people ask what's different about the frosting. It's worth the extra step.
- One pan, no layers. Mix, pour, bake, frost, slice. No stacking, no crumb coat, no torting. This is a true sheet cake built for real life — potlucks, birthdays, Tuesday nights.
- Moist for days. The oil base and sourdough discard work together to keep this cake tender long after baking. It doesn't dry out the way butter-based cakes do.
- Make it your own. Chocolate shavings, berries, festive sprinkles, or a pinch of flaky salt on top — this cake is a blank canvas once it's frosted.
Jump to:
- Quick Look: Sourdough Chocolate Sheet Cake
- Why You'll Love This Recipe
- Ingredients
- How To Make Sourdough Chocolate Sheet Cake
- Easy Substitutions & Variations
- Expert Tips
- What Makes This Recipe Special?
- Sourdough Chocolate Sheet Cake FAQs
- Sourdough Chocolate Cake Troubleshooting Guide
- Storage
- Other Cake Recipes to Try
- Sourdough Chocolate Sheet Cake with Brown Butter Buttercream
Ingredients
- all-purpose flour: The structure base — weighed for accuracy. The batter is thin, and the flour ratio matters.
- cocoa powder: Dutch-process gives you a darker, more intense chocolate flavor and color. Natural cocoa works too — see the substitutions section.
- sourdough discard: The star of the show. Active starter works too — the main thing is that it's at room temperature. This is also what gives the cake its subtle tang and keeps the crumb extra tender.
- cane sugar + brown sugar: The brown sugar adds moisture and a quiet caramel note that deepens the chocolate flavor. Same double-sugar approach I use in my chocolate chunk banana bread.
- vegetable oil: Oil over butter keeps this cake moist for days — critical for a sheet cake that might sit out at a party.
- butter (for browning): You'll start with 142g and end up with about 111g after the water cooks off. The browned milk solids are where all that nutty flavor lives — don't strain them out.
- butter (softened): Combined with the brown butter for a fluffy, creamy base.
- stable consistency.
See recipe card for quantities.
How To Make Sourdough Chocolate Sheet Cake
Note: I bake by weight for accuracy. Cup measurements are approximate and may vary depending on how you scoop.
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.
Easy Substitutions & Variations
Long fermentation: Mix the flour, milk, sourdough starter, and oil together, cover, and refrigerate for 24 hours before adding the remaining ingredients and baking. The extra fermentation time deepens the tang and makes the crumb even more tender.Storage
Cocoa powder: Dutch-process is ideal but natural cocoa works — just add an extra ½ teaspoon baking powder and reduce the baking soda slightly to account for the difference in acidity.
Milk: A full-fat non-dairy milk works well here. Oat milk (full-fat) is a great option.
Dairy-free butter: A plant-based butter works in both the cake and the buttercream. Skip added salt in the buttercream if using — most plant butters are already well salted.
Espresso variation: Add 2 teaspoons of instant espresso powder with the dry ingredients. Same coffee-amplifies-chocolate principle behind my white chocolate espresso blondies — it deepens the chocolate without adding a coffee flavor.
Double chocolate: Fold 1½ cups of chocolate chips into the batter before baking. Walnuts work here too.
Different frosting: Swap the brown butter buttercream for vanilla buttercream or the strawberry buttercream from my strawberry crunch cupcakes — it's a fun, unexpected pairing with a chocolate base.
Expert Tips
Cool completely before frosting. A warm cake melts buttercream on contact. Give it the full cool — use that time to whip up the frosting.
Brown the butter ahead of time. It needs to cool completely before you can use it in the buttercream — at least 2 hours at room temperature, or do it the night before and refrigerate it. Bring it back to room temperature before beating.
Add powdered sugar gradually. Adding it all at once creates a cloud and can leave lumps. Half a cup at a time, with the mixer on low, keeps things tidy and smooth.
Don't overmix the batter. Add the wet ingredients into the dry and stir until just combined. Overmixing develops gluten and can make the cake dense. The same rule applies to my sourdough discard banana muffins — mix just until you stop seeing dry flour.
The batter will look very thin. Don't panic and don't add flour. It bakes up perfectly every time.
What Makes This Recipe Special?
Most chocolate sheet cakes are good. This one has two things working in its favor that most don't: sourdough discard and brown butter.
The discard adds a subtle fermented tang that cuts the sweetness of the cake and keeps the crumb incredibly moist — it's doing the same work it does in my sourdough discard coffee cake and fluffy sourdough discard cinnamon rolls. The brown butter in the frosting adds a nutty, slightly caramelized depth that regular buttercream just doesn't have. Together, they make a sheet cake that tastes like you put in way more effort than you actually did.
Sourdough Chocolate Sheet Cake FAQs
Yes — active starter works just as well here. The main thing is that it's at room temperature when it goes into the batter so it incorporates smoothly.
That's exactly what it's supposed to look like. The oil, eggs, and sourdough discard make for a very fluid batter that bakes up moist and tender. Do not add more flour.
Yes — the cake can be baked, covered, and stored at room temperature for up to 2 days before frosting. The brown butter can be made and refrigerated up to a week ahead. Just bring it back to room temperature before beating it into the buttercream.
Yes. Flash freeze the unfrosted or frosted cake uncovered first, then wrap tightly in plastic wrap followed by aluminum foil. Freeze for up to 6 months. Thaw in the fridge to prevent condensation from ruining the frosting.
Sourdough Chocolate Cake Troubleshooting Guide
| Problem | Cause | Fix |
|---|---|---|
| Dense or sunken cake | Overmixed batter | Stir wet into dry until just combined. |
| Buttercream won't come together | Brown butter too warm | Cool completely before beating — 2 hours minimum. |
| Lumpy buttercream | Powdered sugar added too fast | Add ½ cup at a time on low speed. |
| Cake dried out quickly | Overbaked | Pull when toothpick has just a few moist crumbs. |
| Frosting melted on cake | Cake wasn't fully cool | Always cool completely — minimum 1 hour. |
Storage
- Store in an airtight container in the refrigerator for up to 4 days.
- To freeze: flash freeze uncovered, then wrap in plastic wrap and aluminum foil. Freeze for up to 6 months. Thaw in the refrigerator.
- Pull refrigerated cake out 20–30 minutes before serving so the buttercream softens back to the right texture.
Other Cake Recipes to Try
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!
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