Sourdough Discard Brownies Peanut

My sourdough starter had been neglected for weeks—one of those kitchen experiments that sits in the back of the fridge, forgotten until guilt sets in. Rather than discard it like usual, I wondered what would happen if I baked it into something chocolatey and indulgent. The answer was these brownies, dense and fudgy in a way that felt almost accidental, as if the starter knew exactly where it belonged all along.

I brought a batch to a friend's dinner party, half-joking about the sourdough secret ingredient. Everyone assumed I'd bought them from a bakery—the fudgy interior, the way the peanut butter swirl caught the light. That moment of kitchen pride, watching people take second pieces, made me realize this wasn't just a way to use up starter. It had become something I actually wanted to make.

Ingredients

• Unsalted butter (115 g): Room temperature melts more smoothly with the chocolate, and using unsalted lets you control the salt level precisely.
• Semisweet chocolate chips or chopped chocolate (170 g): Chop larger pieces yourself if you can—they melt more evenly than chips and give a richer texture.
• Sourdough discard (120 g): Use unfed starter that's been sitting in the fridge; the slightly fermented flavor is what makes these special.
• Granulated sugar (200 g): This is your sweetness base, and it also helps create that fudgy crumb structure.
• Large eggs (2): Room temperature eggs incorporate more smoothly and create a silkier batter.
• Vanilla extract (1 tsp): A touch of vanilla rounds out the chocolate without making it taste like vanilla cake.
• All-purpose flour (65 g): Measure by weight if possible—too much flour turns brownies cakey, and these need to stay fudgy.
• Unsweetened cocoa powder (30 g): The Dutch-processed kind gives deeper color, but natural cocoa works too.
• Fine sea salt (1/2 tsp): Salt is your secret weapon, making chocolate taste more like chocolate.
• Creamy peanut butter (80 g): The swirl ingredient—use good quality peanut butter that's not too oily or it'll separate.
• Powdered sugar (1 tbsp, optional): Makes the swirl smoother and adds a touch of sweetness to balance the chocolate.

Instructions

Heat your oven and prepare:

Set oven to 175°C (350°F) and line your 20x20 cm pan with parchment paper, leaving some overhang so you can lift the finished brownies out easily. This step takes two minutes but saves so much frustration later.

Melt chocolate with butter gently:

In a microwave-safe bowl, combine butter and chocolate, melting in 30-second bursts and stirring between each one—this prevents the chocolate from seizing and keeps everything smooth. Let it cool for 3 minutes so the eggs don't scramble when you combine everything.

Whisk the sourdough base:

In a large bowl, whisk together sourdough discard, sugar, eggs, and vanilla until the mixture is pale and slightly thickened, about 1 minute. You'll notice the sugar starts dissolving and the eggs get frothy—that's exactly what you want.

Combine chocolate into the wet mixture:

Pour the cooled chocolate into the egg mixture and whisk until completely smooth and glossy, with no streaks of chocolate visible. This takes about 30 seconds of steady whisking.

Fold in dry ingredients carefully:

Sift the flour, cocoa powder, and salt directly into the bowl and fold with a spatula using as few strokes as possible—overmixing develops gluten and makes brownies tough. Stop the moment you don't see any white flour streaks.

Transfer and smooth the batter:

Pour the batter into your prepared pan and smooth the top with the back of a spatula so it bakes evenly. The batter should look thick and glossy.

Add the peanut butter swirl:

In a small bowl, mix peanut butter with powdered sugar if using, then drop spoonfuls randomly across the batter. Take a skewer or thin knife and drag it through the peanut butter in loose, organic lines—don't overswirl or it'll muddy the effect.

Bake until just set:

Bake for 28–32 minutes; the center should jiggle very slightly when you shake the pan, and a toothpick should come out with moist crumbs clinging to it, not wet batter. Brownies continue cooking as they cool, so slightly underbaked is better than overbaked here.

Cool completely before cutting:

Let the pan sit on a counter for at least 2 hours—rushing this step leads to crumbly, broken brownies. Use the parchment overhang to lift them out, then cut with a sharp, dry knife for clean edges.

Save

There's something almost meditative about using up starter instead of tossing it, turning kitchen abundance into something delicious. These brownies became my answer to the guilt of neglect.

Why Sourdough Discard Works Here

Sourdough starter contains both acid and moisture, both crucial for brownies. The fermented liquid replaces some of the liquid you'd normally use, adding depth that plain eggs and sugar can't achieve. It also interferes slightly with gluten development, which keeps the crumb tender rather than chewy. The tang is so subtle that most people won't identify it—they'll just notice the brownies taste richer somehow.

The Peanut Butter Swirl Technique

The swirl isn't just decoration; it creates little pockets of creamy, salty richness throughout. The key is not overworking it—those loose, organic lines taste better than a fully marbled effect, letting you get both chocolate and peanut butter in each bite. If your peanut butter is too stiff, microwave it for 5 seconds to soften it slightly.

Storage and Serving Ideas

These brownies keep beautifully in an airtight container at room temperature for 4 days, and the flavor actually improves as they sit. A scoop of vanilla ice cream while they're still slightly warm transforms them into something restaurant-worthy, and they're equally good cold straight from the container with a cup of coffee.

• Store in an airtight container to keep them fudgy, not stale.
• A thin dusting of sea salt on top before serving makes the chocolate sing.
• These freeze beautifully for up to a month if you want to stash them away.

Save

These brownies turned my relationship with sourdough starter from obligation to joy. Every time I make them, I'm grateful for the small magic of fermentation and chocolate.

Recipe Guide

→ Can I substitute peanut butter with another spread?

Yes, sunflower seed butter or almond butter work well as alternatives, especially for nut-free preferences.

→ What does sourdough discard add to the batter?

Sourdough discard adds moisture and a subtle tang, enhancing the depth of flavor and tenderness in the brownies.

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

Bake until the center is just set but still moist; a toothpick inserted should come out with moist crumbs, not wet batter.

→ Can I add nuts or chocolate chips for texture?

Absolutely, stirring in chopped nuts or extra chocolate chips adds crunch and boosts richness if desired.

→ Is it necessary to let the brownies cool completely before slicing?

Yes, cooling allows the brownies to firm up, making clean slicing easier and preserving their chewy texture.