Sourdough Discard Brownies Peanut

There's something deeply satisfying about transforming sourdough discard into dessert instead of tossing it out. One Tuesday morning, my starter had been neglected for a week, and rather than feed it again, I found myself staring at a jar of bubbly liquid thinking there had to be a better use. These brownies happened by accident, really—a combination of not wanting waste and craving chocolate at the same time. The sourdough discard adds this incredible moisture and subtle tang that makes them taste almost melted, like fudge in brownie form. That first batch disappeared before my roommate even knew I'd baked them.

I brought these to a potluck last spring, unsure if anyone would even try them since I had to explain what sourdough discard was. By the end of the night, someone was asking for the recipe while holding an empty plate, and honestly, that felt like winning. My friend who claims to be anti-peanut butter desserts came back for seconds, muttering something about how the swirl actually works. Food has this magical way of breaking down defenses when it's made with a little care.

Ingredients

• Unsalted butter (115 g): Melts beautifully with chocolate and won't overpower the cocoa flavor—salted would compete with the peanut butter's savory edge.
• Semisweet chocolate chips or chopped chocolate (170 g): The backbone of fudgy texture; don't skimp on quality here because it makes the difference between dense and dull versus rich and memorable.
• Sourdough discard (120 g): The secret weapon that keeps these brownies impossibly moist for days—use unfed discard right from the jar for maximum tang and moisture.
• Granulated sugar (200 g): Feeds the cocoa richness and balances the slight sourness from the starter perfectly.
• Large eggs (2): Bind everything together and contribute to that fudgy crumb structure we're after.
• Vanilla extract (1 tsp): Rounds out the chocolate without announcing itself; pure vanilla works best here.
• All-purpose flour (65 g): Just enough structure to hold everything together without making them cake-like—measure carefully.
• Unsweetened cocoa powder (30 g): Deepens the chocolate flavor and adds that beautiful bitterness that makes you crave another bite.
• Fine sea salt (1/2 tsp): Awakens the chocolate and tames the sweetness; don't skip this small magic.
• Creamy peanut butter (80 g): The swirl that makes every slice feel special—smooth rather than chunky creates the most beautiful contrast against the dark chocolate.
• Powdered sugar (1 tbsp, optional): Makes the peanut butter swirl a touch sweeter and easier to stripe through the batter without dragging.

Instructions

Prep your workspace:

Preheat your oven to 175°C (350°F) and line an 8x8 inch square pan with parchment paper, letting it overhang the edges slightly so you can lift the whole batch out later without wrestling it.

Melt chocolate with butter:

In a microwave-safe bowl, combine the butter and chocolate chips, then microwave in 30-second bursts, stirring between each one—this prevents seizing and keeps the chocolate silky. Once melted and smooth, let it cool for exactly 3 minutes; you want it warm but not hot when it meets the eggs.

Combine wet ingredients:

In a large bowl, whisk together your sourdough discard, sugar, eggs, and vanilla until everything is pale and well-incorporated—this takes about a minute and creates the structure for your brownies.

Marry chocolate to the mix:

Pour the cooled chocolate mixture into the wet ingredients and whisk gently until completely smooth and glossy with no streaks of chocolate visible.

Fold in dry ingredients carefully:

Sift the flour, cocoa powder, and salt directly into the bowl, then use a spatula to fold everything together with just 10-12 gentle strokes—overmixing develops gluten and makes brownies cake-like instead of fudgy. A few flour streaks are fine.

Pour and spread:

Transfer the batter into your prepared pan and smooth the top with your spatula until it's even, but don't press down too hard.

Create the peanut butter swirl:

In a small bowl, stir together your peanut butter with powdered sugar if using (it makes it easier to swirl), then drop small spoonfuls randomly across the brownie surface. Take a skewer or thin knife and drag it gently through the peanut butter, making zigzag or curved patterns that pull the peanut butter down into the batter without fully mixing.

Bake to fudgy perfection:

Bake for 28-32 minutes—the edges will look set and slightly crispy, but the center should still jiggle slightly when you gently shake the pan. A toothpick inserted in the middle should come out with moist, fudgy crumbs, not wet batter but definitely not dry either.

Cool with patience:

Let the entire pan cool completely at room temperature—this takes about an hour and is crucial because warm brownies will crumble when you cut them. Once cooled, use the parchment paper overhangs to lift the whole block out onto a cutting board and slice into 16 squares.

Pin Recipe

My sister called while I was cooling a batch and asked if she could swing by later—I almost said no because they weren't ready, but something made me say yes anyway. She arrived with her daughter, who announced she doesn't like brownies, then ate two squares while sitting on my kitchen counter. Watching a kid change her mind about something because it tasted genuinely good reminded me why I love cooking in the first place.

Sourdough Discard: The Hero Ingredient

If you've been feeling guilty about your sourdough starter or wondering what to do with all that discard, this is your answer. The unfed discard contains living bacteria and yeast that add subtle complexity to the brownie flavor—it creates this almost tangy undertone that balances the sweetness without tasting sour. Plus, the added moisture from the discard means these brownies stay fudgy for three or four days, sometimes longer, which is remarkable for a baked good. I've learned that discard from a starter that's been sitting out (room temperature) works better than cold discard from the fridge, because the warmer temperature helps it incorporate smoothly.

The Science of Fudgy Brownies

Fudgy brownies live in the tension between underbaked and baked just enough. The key is understanding that carryover cooking happens after you remove them from the oven—the residual heat continues cooking the center for a few minutes even as the edges set. This is why the toothpick test matters: you're looking for moist crumbs, not a clean stick, because that's the signal that the proteins have set enough to support the brownie's structure without overdrying it. The sourdough discard adds fat and moisture that naturally resists overbaking, which means you have a slightly more forgiving window than with traditional brownie recipes.

Customizations and Variations

Once you've made these once, you'll start seeing possibilities everywhere. I've stirred in espresso powder (1 teaspoon) to deepen the chocolate flavor until it tastes almost dangerous, added chopped dark chocolate on top before baking for extra texture, and even swapped the peanut butter for almond butter when someone at a dinner party mentioned allergies. The sourdough discard is flexible enough that it works with all these variations. My personal favorite twist involves a sprinkle of fleur de sel on top right after pulling them from the oven—the salt crystals catch the warm chocolate and create these little moments of brightness. You could also press some cocoa nibs onto the surface before baking if you want an extra crunch factor.

• For nut-free brownies, simply omit the peanut butter swirl or replace it with sunflower seed butter, which swirls beautifully and has a lighter flavor.
• If you don't have semisweet chocolate, dark chocolate makes them more sophisticated and complex, while milk chocolate creates a sweeter, more indulgent version.
• Try baking these in a loaf pan instead of a square pan to create thicker, taller brownies that feel extra substantial and special.

Pin Recipe

These brownies transformed my relationship with sourdough discard from guilt to anticipation—now I actually look forward to my starter getting a little neglected because it means brownie time. They're the kind of dessert that tastes impressive enough to share but simple enough that you'll find yourself making them on random Thursdays just because.

Recipe FAQs

→ What does sourdough discard add to the brownies?

It contributes extra moisture and a subtle tang, enhancing the fudgy texture without overpowering the chocolate flavor.

→ Can I substitute peanut butter with another spread?

Yes, sunflower seed butter works well for a nut-free alternative while maintaining the creamy swirl effect.

→ How do I know when the brownies are done baking?

Check with a toothpick inserted into the center; it should come out with moist crumbs but not wet batter.

→ Is it necessary to melt the butter and chocolate together?

Melting ensures a smooth, glossy chocolate base that blends easily into the batter for uniform richness.

→ Can I add mix-ins for extra texture?

Adding chocolate chips or chopped nuts is a great way to introduce crunch and varying flavors.