These brownies use sourdough starter — fed or discard — in place of some of the liquid in a standard brownie batter. The starter’s mild acidity sharpens the chocolate flavor without making the brownies taste sour. If you keep a starter and hate throwing any away, this is a genuinely good use for it.
Before you start
The two steps that decide whether these brownies succeed are the chocolate melt and the mixing. Melt the butter and chocolate together slowly over a water bath, stirring constantly — if the bowl gets too hot or you stop stirring, the chocolate can seize into a grainy paste that won’t smooth out. Once you add the flour and cocoa, switch to a spatula and fold only until the dry streaks disappear. Overmixing at that stage develops gluten and pushes the texture toward cakey rather than chewy, which is the opposite of what you want here.
Ingredient notes
- Bittersweet chocolate (70% cocoa): The percentage matters. A lower-cocoa chocolate brings more sugar and less fat, which changes the set and the flavor. Stick close to 70% for the balance the recipe is built around.
- Sourdough starter: Both fed starter and unfed discard work. A very active, recently fed starter will produce a slightly lighter crumb; older discard gives a more pronounced tang. Either is fine — just make sure it’s at room temperature so it blends smoothly into the batter.
- Brown sugar: Packed brown sugar adds a faint molasses note that works well with dark chocolate. Don’t substitute all-white sugar unless you have to; the swap flattens the flavor noticeably.
Common problems and fixes
- Brownies sink in the middle after baking: This usually means underbaking. The toothpick test is the reliable check — pull the pan when the toothpick comes out with a few moist crumbs, not wet batter. A sunken center that’s still raw in the middle needs another 3–5 minutes.
- No glossy top: The shiny crust forms when the sugar and eggs are whisked together well before the dry ingredients go in. If you rush that step or the eggs are cold, the top bakes up matte and slightly dull. Room-temperature eggs make a real difference.
- Brownies stick and tear when cutting: Parchment overhang is there for a reason — use it. Beyond that, let the brownies cool completely before cutting, and use a sharp knife wiped clean between slices. Cutting warm brownies, especially in a larger batch, turns clean squares into a mess.
- Batter looks broken or greasy after adding eggs: This happens when the chocolate mixture is still too hot when the eggs go in. Let the melted chocolate and sugar mixture cool for 5 minutes before beating in the eggs. Whisk each egg in fully before adding the next — the batter will come together.
- Edges overbake while the center is still soft: An 8×8 pan is specified for a reason. A larger pan spreads the batter thinner and the edges set and dry out before the center is done. Skip the larger pan — not worth the uneven result — and bake in the size the recipe calls for.
Sourdough Brownies
Equipment
- 8x8-inch baking pan
- Mixing Bowls
- Whisk
- Spatula
- Oven
Ingredients
- 1 cup unsalted butter preferably organic
- 10 ounces bittersweet chocolate good quality, 70% cocoa
- ¾ cup granulated sugar
- ¾ cup brown sugar packed
- 3 large eggs at room temperature
- 1 cup sourdough starter discard or fed
- 1 teaspoon vanilla extract
- ½ cup all-purpose flour sifted
- ¼ cup cocoa powder unsweetened
- ½ teaspoon salt
Instructions
- Preheat the oven to 350°F (175°C). Grease an 8x8 inch baking pan, and line it with parchment paper, allowing some overhang for easy removal.
- In a mixing bowl, melt the butter and bittersweet chocolate over a simmering water bath. Stir consistently until smooth, ensuring the chocolate doesn't seize.
- Remove the bowl from heat and whisk in both sugars until fully integrated and the mixture appears glossy.
- Beat in the eggs one at a time, ensuring each one is well incorporated before adding the next.
- Stir in your sourdough starter and vanilla extract until the batter is smooth.
- Incorporate the flour, cocoa powder, and salt into the wet ingredients. Fold the dry ingredients using a spatula, taking care not to over-mix.
- Pour the batter into the prepared pan, smoothing the top with your spatula.
- Bake in the preheated oven for 25-30 minutes. The brownies should appear set on top with a slight crackling. To ensure doneness, insert a toothpick which should come out with a few moist crumbs.
- Remove from the oven and let cool completely in the pan before lifting out and cutting into 12 pieces.
Notes
Tammy’s Tips
- For a creative twist, add 1 cup of chopped nuts or chocolate chunks to the batter before baking.
- To adapt for a gluten-free option, swap the all-purpose flour with almond or coconut flour, adjusting for moisture as needed.
- Enhance flavors by using a hint of espresso powder in the brownie batter.
Nutrition
FAQ
Can I double this recipe to make a bigger batch?
Yes — doubling the recipe works reliably. Use a 9×13-inch pan and start checking for doneness at 30 minutes, since the thicker batter in a wider pan can take up to 35 minutes; use the toothpick test rather than the clock.
Can I make these a day ahead?
Yes, and they’re actually better the next day. Store the uncut slab tightly wrapped at room temperature overnight — the texture firms up and the chocolate flavor deepens. Cut them the day you plan to serve them.
My sourdough starter has been in the fridge for a week. Is it still okay to use?
It’s fine to use straight from the fridge without feeding first. Bring it to room temperature before adding it to the batter so it incorporates evenly; cold starter can cause the batter to seize slightly around it.
How do I know when the brownies are done without overbaking them?
The toothpick test is the most reliable method: insert it into the center and look for a few moist crumbs clinging to it, not wet batter. The top should look set and show a slight crackle; if it still looks glossy and wet in the center, give it another 3 minutes and test again.
More sweet things to bake
- White Chocolate Matcha Brownies
- Dark Chocolate Espresso Tartlets
- Nutty Maple Blondies with Tahini
- Dark Chocolate Brown Butter Tart