Fudgy Chocolate Peanut Butter Swirl Brownies

Quick Recipe Version (TL;DR)

• Yield: 16 brownies
• Prep Time: 20 minutes
• Cook Time: 28–32 minutes
• Total Time: 50 minutes

Quick Ingredients

• 1/2 cup (113 g) unsalted butter
• 4 oz (113 g) semisweet or dark chocolate, chopped
• 1 cup (200 g) granulated sugar
• 1/4 cup (50 g) light brown sugar, packed
• 2 large eggs + 1 large egg yolk, room temperature
• 2 tsp pure vanilla extract
• 3/4 cup (90 g) all-purpose flour
• 1/4 cup (25 g) unsweetened cocoa powder
• 1/2 tsp fine sea salt
• 1/2 tsp instant espresso powder (optional)
• 1/2 cup (90 g) semisweet chocolate chips (optional)
• 1/2 cup (130 g) creamy peanut butter
• 1/4 cup (30 g) powdered sugar
• 1/2 tsp vanilla extract (for swirl)
• 2–3 tbsp milk or heavy cream, as needed
• Flaky sea salt for topping (optional)

Do This

• 1. Preheat oven to 350°F (175°C). Line a 9-inch square pan with parchment, leaving overhang.
• 2. Melt butter and chopped chocolate together until smooth; cool slightly.
• 3. Whisk sugars, eggs, yolk, and vanilla; whisk in melted chocolate, then fold in dry ingredients and chocolate chips.
• 4. Stir peanut butter, powdered sugar, vanilla, and enough milk/cream to make a thick but spoonable mixture.
• 5. Spread about 2/3 of brownie batter in pan, dollop peanut butter mixture on top, then spoon remaining batter between dollops.
• 6. Swirl gently with a knife or skewer to create marbled ribbons without overmixing.
• 7. Bake 28–32 minutes until edges are set and center is just slightly wobbly. Cool, slice, and enjoy.

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Why You’ll Love This Recipe

• Super fudgy brownies with rich chocolate flavor and shiny, crinkly tops.
• Sweet, creamy peanut butter ribbons baked right into every bite.
• Marbled swirl looks bakery-level impressive but is easy to do at home.
• One bowl for the brownies, simple pantry ingredients, and ready in under an hour.

Grocery List

• Produce: None
• Dairy: Unsalted butter, milk or heavy cream (optional, for swirl)
• Pantry: Semisweet or dark chocolate, granulated sugar, light brown sugar, all-purpose flour, unsweetened cocoa powder, fine sea salt, instant espresso powder (optional), creamy peanut butter, powdered sugar, vanilla extract, chocolate chips (optional), flaky sea salt (optional)

Full Ingredients

For the Brownie Batter

• 1/2 cup (113 g) unsalted butter, cut into pieces
• 4 oz (113 g) semisweet or dark chocolate (50–60% cocoa), finely chopped
• 1 cup (200 g) granulated sugar
• 1/4 cup (50 g) light brown sugar, packed
• 2 large eggs, room temperature
• 1 large egg yolk, room temperature
• 2 tsp pure vanilla extract
• 3/4 cup (90 g) all-purpose flour, spooned and leveled
• 1/4 cup (25 g) unsweetened cocoa powder
• 1/2 tsp fine sea salt
• 1/2 tsp instant espresso powder (optional, enhances chocolate flavor)
• 1/2 cup (90 g) semisweet chocolate chips or chunks (optional, for extra fudginess)

For the Peanut Butter Swirl

• 1/2 cup (130 g) creamy peanut butter (not natural-style that separates, if possible)
• 1/4 cup (30 g) powdered sugar
• 1/2 tsp pure vanilla extract
• 2–3 tbsp milk or heavy cream, as needed to thin to a thick, pourable consistency
• Pinch of salt (only if your peanut butter is unsalted)

Optional Topping

• Flaky sea salt, for sprinkling on top after baking

Step-by-Step Instructions

Step 1: Prep the Pan and Preheat the Oven

Preheat your oven to 350°F (175°C) with a rack in the center position. Lightly grease a 9-inch (23 cm) square baking pan with butter or nonstick spray. Line the pan with parchment paper, leaving an overhang on two opposite sides to create a sling. This makes it easy to lift the brownies out later for clean slicing. Lightly grease the parchment as well. Set the pan aside while you prepare the batter.

Step 2: Melt the Butter and Chocolate

In a medium heatproof bowl, combine the unsalted butter and chopped semisweet or dark chocolate. Melt together using one of the following methods:

Microwave method: Heat in 20–30 second bursts, stirring well after each, until completely smooth and glossy. This usually takes about 1–1½ minutes total.

Stovetop method: Place the bowl over a saucepan of barely simmering water (double-boiler style), making sure the bottom of the bowl does not touch the water. Stir until melted and smooth.

Once melted, set the mixture aside to cool for 5 minutes. It should be warm but not hot when you add it to the eggs.

Step 3: Make the Brownie Batter

In a large mixing bowl, whisk together the granulated sugar and light brown sugar. Add the 2 large eggs and 1 egg yolk. Whisk vigorously for about 1 minute until the mixture looks thick, lighter in color, and slightly ribbony. This step helps create that glossy, crackly top.

Whisk in the vanilla extract. Slowly pour the slightly cooled melted chocolate-butter mixture into the egg mixture, whisking constantly until fully combined and shiny.

In a separate small bowl, whisk together the flour, cocoa powder, salt, and instant espresso powder (if using). Sprinkle the dry ingredients over the wet ingredients and use a spatula to fold gently just until no dry streaks remain. If using chocolate chips or chunks, fold them in now. The batter will be thick and glossy—avoid overmixing to keep the brownies tender.

Step 4: Mix the Peanut Butter Swirl

In a medium bowl, add the creamy peanut butter, powdered sugar, vanilla extract, and a pinch of salt if your peanut butter is unsalted. Stir together with a spoon or small whisk. Gradually add 2–3 tablespoons of milk or heavy cream, 1 tablespoon at a time, stirring after each addition, until you have a thick but spoonable mixture. It should be loose enough to dollop and swirl, but not so runny that it disappears into the batter. Set aside.

Step 5: Assemble the Batter and Swirl

Give the brownie batter a final gentle stir. Pour about two-thirds of the brownie batter into the prepared pan and spread it into an even layer with a spatula, reaching all the corners.

Using a spoon, drop generous dollops of the peanut butter mixture all over the surface of the batter. Spoon the remaining brownie batter in between and on top of the peanut butter dollops, leaving some peanut butter visible.

Take a thin knife or skewer and drag it through the batter in gentle, looping motions to create a marbled pattern. Aim for 5–7 passes across the pan; avoid over-swirling or the two mixtures will blend together instead of forming distinct ribbons.

Step 6: Bake Until Fudgy

Place the pan in the preheated oven and bake for 28–32 minutes. The edges should look set and slightly pulled away from the sides of the pan, and the center should look just set with a slight jiggle when you gently shake the pan. A toothpick inserted 2 inches from the edge should come out with a few moist crumbs (not wet batter); the center may show a bit more moisture, which is ideal for fudgy brownies.

If desired, as soon as the brownies come out of the oven, sprinkle a small pinch of flaky sea salt evenly over the top to contrast with the sweetness.

Step 7: Cool, Slice, and Serve

Place the pan on a wire rack and let the brownies cool in the pan for at least 30–45 minutes. For the cleanest slices and the fudgiest texture, let them cool completely (1–2 hours) or even chill briefly in the refrigerator.

Once cooled, use the parchment sling to lift the brownies out of the pan and onto a cutting board. Use a long, sharp knife to cut into 16 squares, wiping the knife clean between cuts for neat edges. Serve at room temperature, or slightly warmed so the peanut butter pockets soften and the chocolate becomes extra gooey.

Pro Tips

• Do not overbake: Brownies continue to set as they cool. Pull them when the center is just barely set for the fudgiest texture.
• Measure flour carefully: Too much flour makes cakey brownies. Spoon into the cup and level, or use a scale for accuracy.
• Use room-temperature eggs: They incorporate more easily and help create a shiny, crackly top.
• Control the swirl: Fewer, deliberate swirls give distinct marbling; too many passes will blend the peanut butter into the batter.
• Chill for ultra-clean slices: For perfect squares (especially for gifting or parties), chill the baked, cooled slab for 30–45 minutes before cutting.

Variations

• Salted Peanut Butter Brownies: Use salted peanut butter and finish with a generous sprinkle of flaky sea salt on top for a sweet-salty contrast.
• Extra-Chocolate Swirl: Add 1/4 cup (25 g) extra cocoa powder and an additional 2 tbsp butter to the brownie batter, and stir 1/4 cup mini chocolate chips into the peanut butter mixture.
• Peanut Butter & Jam Swirl: Dollop 1/4–1/3 cup of your favorite thick berry jam alongside the peanut butter mixture and swirl them together for a PB&J twist.

Storage & Make-Ahead

Once completely cool, store the brownies in an airtight container at room temperature for up to 3 days. For slightly longer storage (4–5 days), refrigerate them; let them come to room temperature or warm briefly before serving so the peanut butter softens. To freeze, wrap individual brownies tightly in plastic wrap, then place in a freezer bag or airtight container and freeze for up to 3 months. Thaw at room temperature for 1–2 hours or warm in the microwave in 10–15 second bursts until just soft and slightly warm.

Nutrition (per serving)

Approximate values per brownie (1 of 16): about 260 calories, 4 g protein, 30 g carbohydrates, 14 g fat, 7 g saturated fat, 1 g fiber, and 20 g sugar. These numbers are estimates and will vary based on specific brands and optional additions (like extra chocolate chips or flaky salt).