Peanut Butter Swirl Brownies
Fudgy cocoa brownies marbled with salty peanut butter.
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Before You Start
A fudgy one-bowl brownie base with ribbons of sweetened peanut butter dragged through the top. The swirl is not just for looks: it bakes into soft, salty seams that cut the chocolate. Use standard smooth peanut butter, not the natural kind that splits.
Instructions
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1
Heat the oven to 175°C / 350°F. Line a 20 cm (8-inch) square tin with baking paper, leaving an overhang.
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2
Whisk the melted butter with the granulated sugar and cocoa until glossy. Whisk in the eggs one at a time, then the vanilla, and keep whisking for a minute for a shiny top.
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3
Fold in the flour and salt with a spatula, stopping the moment the flour disappears. Overmixing makes brownies cakey.
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4
Spread the batter in the tin. Warm the peanut butter for 20 seconds and stir in the powdered sugar until pourable.
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5
Dot the peanut butter over the batter in spoonfuls, then drag a knife through it in an S shape a few times. Two or three passes is plenty, more and the swirl turns muddy.
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6
Bake for 28 to 34 minutes, until the edges are set and a skewer in the middle comes out with moist crumbs. Cool completely in the tin before lifting out and cutting.
💡 Baker's tips
- Cool them fully, ideally a couple of hours. Warm brownies tear instead of slicing cleanly.
- Flaky salt over the peanut butter just before baking makes both flavours sharper.
🔀 Make it your own
- Swap the peanut butter for biscoff, tahini or almond butter, same quantity.
- Press 100 g chocolate chunks into the top before baking for a heavier hit.
📦 Storing & freezing
Airtight at room temperature for 4 days, and they get fudgier on day two. Freeze cut squares for 3 months.
❓ Frequently asked
How many grams is a cup of peanut butter?
About 256 g per US cup, so the ½ cup here is roughly 128 g. The peanut butter converter will rescale it for you.
Can I use natural peanut butter?
It works but the oil can separate and leave greasy patches. Stir it very well first, or use a standard emulsified peanut butter for a cleaner swirl.
Baking in a different unit? Use the cups ↔ grams converter or the recipe scaler to halve or double this recipe.
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