🍫🥜 Gooey Sourdough Discard Chocolate Peanut Butter Bars — Swirled, Chewy & Ready in About an Hour

🍫🥜 Gooey Sourdough Discard Chocolate Peanut Butter Bars

Swirled, chewy, and dangerously easy to eat straight from the pan.

Makes 16 Bars  •  Beginner Friendly  •  Discard-Powered  •  Ready in ~1 Hour

Chocolate and peanut butter are the greatest double act in baking history, and these sourdough discard chocolate peanut butter bars let them steal the show while your discard does the quiet hero work underneath. One bowl, one pan, zero mixer required — and a swirl on top so pretty people will assume you spent all afternoon on them.

Here's the thing nobody tells you about discard: it's not just for pancakes and crackers. Stirred into a rich peanut butter blondie base with a dark chocolate swirl, discard adds a gentle tang that cuts the sweetness and keeps the crumb soft and chewy for days. These bars taste like a peanut butter cup grew up, got a sourdough education, and came home to show off.

If your discard jar is overflowing and your sweet tooth is calling, this is the recipe. Let's bake.

Why You'll Love These Chocolate Peanut Butter Bars

• ✔ One bowl, one pan, no mixer — the whole thing comes together in about 15 minutes of actual work.
• ✔ Uses a full cup of discard — a proper dent in that jar, not a token tablespoon.
• ✔ Chewy, gooey, and swirled — a peanut butter blondie base with ribbons of dark chocolate running through every bite.
• ✔ That sourdough tang — just enough to balance the sweetness and keep the bars from tasting one-note.
• ✔ Stays soft for days — somehow even better on day two, if they survive that long.
• ✔ Freezer-friendly — bake a double batch and stash half for future you.
• ✔ Kid-approved, grown-up approved — lunchboxes, bake sales, midnight snacks, all covered.

Sourdough Discard Chocolate Peanut Butter Bars Ingredients

Peanut Butter Blondie Base

• 120 g sourdough discard (about ½ cup, unfed is perfect)
• 130 g creamy peanut butter (about ½ cup, the regular kind — not the runny natural style)
• 115 g unsalted butter, melted (about ½ cup)
• 200 g light brown sugar (about 1 cup, packed)
• 50 g granulated sugar (about ¼ cup)
• 2 large eggs, room temperature
• 5 g vanilla extract (about 1 teaspoon)
• 190 g all-purpose flour (about 1½ cups)
• 3 g baking powder (about ½ teaspoon)
• 3 g fine sea salt (about ½ teaspoon)
• 100 g roasted peanuts, roughly chopped (about ⅔ cup)

Chocolate Swirl

• 170 g dark chocolate chips or chopped dark chocolate (about 1 cup)
• 30 g creamy peanut butter (about 2 tablespoons)
• 15 g unsalted butter (about 1 tablespoon)
• Flaky sea salt, for sprinkling on top

🥣 Step 1: Heat the Oven and Prep the Pan

Preheat your oven to 175°C (350°F). Line a 20 cm (8-inch) square baking pan with parchment paper, leaving overhang on two sides so you can lift the whole slab out later. Give the parchment a light smear of butter or a quick spritz of oil — future you, trying to peel a stuck bar off the pan, will be grateful.

Beginner Tip: A metal pan gives you the chewiest edges. Glass works too, but add a couple of extra minutes to the bake since glass heats more slowly.

🥜 Step 2: Mix the Peanut Butter Base

In a large bowl, whisk the melted butter, peanut butter, brown sugar, and granulated sugar together until smooth and glossy — about a minute of honest whisking. Add the eggs one at a time, whisking well after each, then stir in the vanilla and the sourdough discard. The mixture should look like thick, silky caramel.

Now fold in the flour, baking powder, and salt with a spatula, just until you can't see dry flour anymore. Stir in the chopped peanuts last. Do not overmix — a few streaks of flour are fine; they'll disappear in the oven, and overmixed bars turn tough instead of chewy.

Pro-Level Move: If your discard is straight from the fridge and extra thick, let it sit on the counter for 20 minutes first. Cold, stiff discard is harder to fold in evenly.

🍫 Step 3: Make the Chocolate Swirl

Melt the dark chocolate, peanut butter, and butter together in a microwave-safe bowl in 20-second bursts, stirring between each, until smooth and pourable. Or melt them gently in a small saucepan over low heat, stirring constantly. Either way, stop as soon as it's smooth — overheated chocolate goes grainy and sulky.

Beginner Tip: Want a stronger peanut butter presence in the swirl? Swap the 2 tablespoons of peanut butter in the swirl for crunchy peanut butter — the little peanut bits look gorgeous on top.

🌀 Step 4: Layer, Swirl, and Bake

Spread the peanut butter batter evenly into your prepared pan. Dollop spoonfuls of the warm chocolate mixture all over the top, then drag a butter knife or skewer through the dollops in lazy figure-eights to create the swirl. Don't overdo it — three or four passes is plenty. You want bold ribbons of chocolate, not a muddy blend.

Sprinkle flaky sea salt over the top and bake for 28–32 minutes, until the edges are set and lightly golden and the centre still looks just slightly soft when you jiggle the pan. A toothpick poked into the centre should come out with moist crumbs, not wet batter.

Pro-Level Move: Pull the pan at 28 minutes even if the centre looks a touch underdone. The bars keep cooking in the hot pan for a few minutes after they leave the oven, and that carryover heat is exactly what gives you the gooey middle.

✂️ Step 5: Cool, Slice, and Try Not to Eat Them All

Let the bars cool in the pan for at least 20 minutes, then lift the whole slab out by the parchment overhang and cool on a rack for another 20 minutes before slicing. Warm bars slice messily (deliciously messily, but messily) — if you want clean squares, wait until they're fully cool and use a sharp knife wiped clean between cuts.

Cut into 16 squares. Or 9 generous ones. We don't judge portion sizes around here.

👩🍳 Squirrelly Girl Baker's Tips

1. 🥜 Use regular peanut butter, not natural. The stabilised kind (the one that doesn't separate) gives these bars their structure. Runny natural peanut butter makes the batter greasy and the bars won't set properly.

2. 🍫 Go dark on the chocolate. Semi-sweet or dark chocolate (60% cocoa or higher) balances the sweet peanut butter base. Milk chocolate tips the whole pan into sugar-overload territory.

3. 🧂 Don't skip the flaky salt. That salty crunch on top is what makes people close their eyes after the first bite. It's a tiny step with an outsized payoff.

4. 📏 Measure the discard, don't eyeball it. A full cup is a lot of liquid — too much and the bars stay gummy in the middle; too little and you lose the tang. Level it off in the measuring cup.

5. 🔪 Chill before slicing for bakery-clean edges. Pop the cooled slab in the fridge for 30 minutes, then slice with a hot, dry knife. You'll get those sharp, swirl-showing squares that look like they came from a bakery case.

🧊 Make It Ahead

These bars keep beautifully. Store them in an airtight container at room temperature for up to 4 days — the discard keeps the crumb soft far longer than a regular blondie. In the fridge they'll last a week (let them come back to room temperature before eating, or warm one for 10 seconds in the microwave).

To freeze, slice the cooled bars, stack them with parchment between the layers, and seal in a freezer bag for up to 3 months. Thaw at room temperature for about an hour, or microwave a single bar for 15 seconds for that just-baked gooeyness. The swirl holds up perfectly after freezing.

🚨 Chocolate Peanut Butter Bars Troubleshooting

Bars came out cakey instead of chewy

You probably overmixed the batter or added a little too much flour. Next time, fold the flour in gently and stop the second it disappears — and spoon your flour into the measuring cup rather than scooping from the bag, which packs it down.

The swirl disappeared into the batter

The chocolate mixture was either too hot or you swirled too many times. Let the chocolate cool for a couple of minutes until it thickens slightly, and keep the swirling to a few lazy passes. Bold dollops, light hands.

Bars are gooey in the middle even after cooling

They were likely underbaked by a few minutes, or the pan was too small and the batter too thick. Bake until the edges are set and a toothpick comes out with moist crumbs, and stick to the 20 cm (8-inch) square pan so the thickness is right.

Bars crumble when I slice them

They were still too warm. Let the slab cool completely — or chill it — before cutting, and use a sharp knife rather than pressing down with a dull one.

The peanut flavour is too mild

Some peanut butters are shy. Next time, use a roasted, full-flavour peanut butter, bump the base peanut butter up by 2 tablespoons, and add the chopped peanuts — they carry a lot of the peanut punch.

⚠️ Baker's Warning

Fair warning: these bars have a side effect. Once your household discovers the pan exists, you will be asked to make them again. And again. And again. You are now officially the person who makes those bars — the ones people request by name and hover near at gatherings. There is no going back. Bake accordingly.

🐿️ Ready to Bake Better Sourdough?

Every great discard recipe starts with a starter that's actually alive and kicking — and if yours is sluggish, tired, or still just a dream, we've got you.

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👉 Get your Squirrelly Girl Sourdough Starter flakes here and turn that discard jar into a baking machine.

Love chewy discard bakes? Our chewy sourdough discard blondies are the brown-butter cousin of these bars, and our soft sourdough discard peanut butter cookies use the same one-bowl, zero-waste spirit in cookie form.

❓ FAQ: Sourdough Discard Chocolate Peanut Butter Bars

Can I use active starter instead of discard?

Yes — active starter works exactly the same way in this recipe. Discard is the classic choice because it's what you have on hand, but if your starter is freshly fed and bubbly, go for it. The bars will taste the same.

Can I make these bars without peanut butter?

You can swap in almond butter or sunflower seed butter cup-for-cup, though the flavour will shift. Avoid runny natural-style butters either way — the thicker, stabilised kind is what holds the bars together.

Do the bars taste sour?

Not really. The discard adds a gentle background tang that balances the sweetness — most people can't identify it as sourdough at all. If your discard is very old and sharp, the tang will be more noticeable, but still pleasant against the chocolate.

Can I add oats or other mix-ins?

Absolutely. A handful of rolled oats, extra chocolate chips, or a swirl of jam on top all work. Keep total add-ins under about a cup so the bars still hold together when sliced.

Why did my bars sink in the middle?

Usually it's underbaking or opening the oven door too early. Bake until the edges are set and the centre only wobbles slightly, and resist peeking before the 25-minute mark — the bars need that undisturbed heat to set their structure.

❤️ Happy Baking!

Chocolate. Peanut butter. Sourdough discard.

Three things that had no business being this good together — and yet here we are.

Go bake a pan. Swirl it like you mean it. Eat one warm.

Then hide the rest, because they will disappear.

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