Fudgy, decadent chocolate brownies swirled with a creamy, salty-sweet peanut butter batter. This mashup of two classics creates the most indulgent, crowd-pleasing dessert square.
Why choose between chocolate and peanut butter when you can have both in every bite? These brownies start with an incredibly rich, one-bowl fudgy chocolate base. A simple, creamy peanut butter mixture is then swirled on top, creating pockets of salty-sweet flavor that perfectly complement the deep chocolate.
The result is a brownie that’s visually stunning, supremely moist, and hits all the right notes of sweet, salty, and decadent. They’re surprisingly easy to make but look and taste like they came from a professional bakery, making them the ultimate treat for any occasion.
The Science of the Swirl & Fudgy Texture
The magic of these brownies lies in two areas: fat content and viscosity. The fudgy brownie base gets its dense, moist texture from a higher fat-to-flour ratio, using both butter and chocolate, and minimal leavening. This creates a batter that sets firmly but remains tender.
The peanut butter swirl is engineered to have a slightly thicker consistency than the brownie batter. This difference in viscosity allows the two batters to remain distinct when swirled together with a knife or skewer. As they bake, the peanut butter mixture softens and sinks slightly but doesn’t fully incorporate, creating those beautiful marbled pockets.
The salt in the peanut butter layer also heightens the flavor of the chocolate, making it taste even richer through the principle of taste contrast. This careful balance ensures every square delivers the perfect ratio of chocolate to peanut butter.
Ingredients
For the Fudgy Brownie Base:
- ½ cup (1 stick / 113g) unsalted butter
- 6 oz (170g) semi-sweet chocolate, chopped
- ¾ cup (150g) granulated sugar
- ⅓ cup (70g) packed brown sugar
- 2 large eggs + 1 egg yolk, room temperature
- 1 teaspoon vanilla extract
- ½ cup (63g) all-purpose flour
- 2 tablespoons unsweetened cocoa powder
- ½ teaspoon salt
For the Peanut Butter Swirl:
- ½ cup (125g) creamy peanut butter
- 3 tablespoons powdered sugar
- 1 tablespoon all-purpose flour
- 1 tablespoon milk or cream
- ¼ teaspoon vanilla extract
- Pinch of salt
Instructions
1. The Melted Chocolate & Butter: In a medium heatproof bowl set over a saucepan of simmering water (or using a microwave in short bursts), melt the butter and chopped chocolate together. Stir until completely smooth and glossy. Remove from heat and let cool slightly.
2. The Thickened Brownie Batter: Whisk the granulated sugar, brown sugar, eggs, egg yolk, and vanilla into the slightly cooled chocolate mixture until the batter is thick, smooth, and slightly paler in color. Gently fold in the flour, cocoa powder, and salt until just combined.
3. The Spread Brownie Base: Line an 8×8 inch baking pan with parchment paper. Pour the brownie batter into the pan and use a spatula to spread it into an even layer.
4. The Mixed Peanut Butter Swirl: In a small bowl, stir together the peanut butter, powdered sugar, flour, milk, vanilla, and salt until completely smooth and slightly thickened.
5. The Dolloped & Ready-to-Swirl Pan: Drop spoonfuls of the peanut butter mixture randomly over the surface of the brownie batter.
6. The Swirled Pan Before Baking: Use a knife or a skewer to gently swirl the peanut butter dollops into the brownie batter. Drag the tool in wide arcs and figure-eights to create a marbled pattern, being careful not to over-mix.
7. The Baked & Cooled Brownies: Bake at 350°F (175°C) for 25-30 minutes, until the edges are set and a toothpick inserted into a chocolatey part comes out with a few moist crumbs. The center should still look slightly soft. Let cool completely in the pan on a wire rack.
8. The Cut & Served Brownies: Once completely cool, lift the brownie slab from the pan using the parchment paper. Place on a cutting board and slice into squares with a sharp knife.
Pro-Tips for Brownie Perfection
- Don’t Overmix the Batter: Once you add the flour, fold gently until just combined to avoid developing gluten, which would make the brownies cakey.
- Cool the Chocolate Slightly: Adding eggs to very hot chocolate can cook them. Let the mixture cool for 5-10 minutes.
- Room Temperature Eggs: They incorporate more easily and help create a shiny, crackly top.
- Consistent Peanut Butter: Use a standard, creamy commercial peanut butter (not natural/oily) for the most reliable swirl consistency.
- Swirl, Don’t Mix: The goal is a marbled effect. Use a gentle hand and make just 4-5 passes with the knife.
- Undercook Slightly: For the fudgiest texture, err on the side of under-baking. The brownies will continue to set as they cool.
- Cool Completely: Cutting warm brownies leads to a messy, crumbly result. Patience is key for clean squares.
- Storage: Store in an airtight container at room temperature for 3 days, or freeze for up to 3 months.
- Flavor Boost: Add ½ cup of chocolate chips to the brownie batter, or a pinch of espresso powder to deepen the chocolate flavor.
- Serving: For an extra treat, serve slightly warm with a scoop of vanilla ice cream.
These Peanut Butter Brownies are a guaranteed crowd-pleaser and a testament to a perfect flavor pairing.
