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Peanut Butter Swirl Brownies

Karina Kari
These Peanut Butter Swirl Brownies are a perfect blend of fudgy chocolate and creamy peanut butter.
In just under an hour, you’ll have a batch of rich, satisfying brownies that are quick to make and sure to please.
Packed with protein from the peanut butter and eggs, they’re a decadent yet slightly wholesome treat.
Prep Time 15 minutes
Cook Time 30 minutes
Total Time 45 minutes
Course Dessert
Cuisine American
Servings 16 brownies

Equipment

  • 8×8-inch pan (1)
  • Parchment paper (1 sheet)
  • Large mixing bowl (1)
  • Medium mixing bowl (1)
  • Small mixing bowl (1)
  • Whisk (1)
  • Knife – 1
  • Cooling rack (1)

Ingredients
  

For the Brownies:

  • 90 g all-purpose flour
  • 200 g granulated sugar
  • 110 g light brown sugar
  • 40 g unsweetened cocoa powder
  • ½ teaspoon fine sea salt
  • ½ teaspoon baking powder
  • 170 g unsalted butter melted
  • 3 large eggs
  • 1 teaspoon vanilla extract

For the Peanut Butter Swirl:

  • 125 g creamy peanut butter
  • 30 g unsalted butter melted
  • 30 g powdered sugar
  • 1 teaspoon vanilla extract
  • ¼ teaspoon fine sea salt

Instructions
 

  • Prepare Your Baking Pan: Start by preheating your oven to 350°F (180°C).
    While the oven is warming, take an 8×8-inch baking pan and grease it lightly with butter or non-stick spray to prevent sticking.
    Then, line the pan with parchment paper, ensuring there’s an overhang on all sides.
    This overhang will make it much easier to lift the brownies out once baked, giving you neat, clean squares without any fuss.
  • Combine the Dry Ingredients: In a large mixing bowl, sift together 90 g of all-purpose flour, 40 g of unsweetened cocoa powder, ½ teaspoon of fine sea salt, and ½ teaspoon of baking powder.
    Once sifted, add 200 g of granulated sugar and 110 g of light brown sugar.
    Whisk everything together until evenly mixed.
    This ensures that your brownie base has a consistent texture, and the cocoa and sugar are evenly distributed for maximum flavor.
  • Mix the Wet Ingredients: In a medium bowl, combine 170 g of melted unsalted butter, 3 large eggs, and 1 teaspoon of vanilla extract.
    Whisk vigorously until the mixture is smooth and slightly frothy.
    The eggs will help give the brownies a rich structure, while the melted butter adds moisture and deep, buttery flavor.
    The vanilla enhances the chocolate and peanut butter aromas, making your brownies irresistible.
  • Incorporate Wet and Dry Ingredients: Gradually add the wet mixture to the dry ingredients.
    Using a spatula or wooden spoon, fold the ingredients together gently until just combined.
    Avoid overmixing, as this can make the brownies tough.
    The batter should be thick, glossy, and slightly sticky.
    Set this mixture aside while you prepare the peanut butter swirl.
  • Prepare the Peanut Butter Swirl: In a small bowl, whisk together 125 g of creamy peanut butter, 30 g of melted unsalted butter, 30 g of powdered sugar, 1 teaspoon of vanilla extract, and ¼ teaspoon of fine sea salt.
    Stir until smooth and fully combined, creating a creamy, pourable peanut butter mixture.
    This step is key to getting a luscious, marbled swirl throughout the brownies.
  • Layer the Brownie Batter: Drop large spoonfuls of the chocolate brownie batter randomly into your prepared pan.
    Don’t worry about spreading it evenly—this irregular placement will help create the beautiful marbled effect.
    Then, add random spoonfuls of the peanut butter mixture over the chocolate batter.
    Finally, use any remaining chocolate batter to fill in bare spots or to lightly top the peanut butter sections.
    The layering creates depth in flavor and a stunning visual pattern once baked.
  • Create the Swirl Pattern: Take a knife or a skewer and gently swirl the batters together.
    Move the knife in a figure-eight or circular motion, dragging it lightly through the chocolate and peanut butter.
    Avoid over-swiping; the goal is to create a beautiful marbled effect, not to fully blend the two batters.
    This step gives the brownies their signature swirl and ensures each bite has a mix of chocolate and peanut butter.
  • Bake the Brownies: Place the pan in the preheated oven on the center rack.
    Bake for 30–35 minutes, checking doneness at the 30-minute mark.
    To test, insert a toothpick into the center it should come out with a few moist crumbs clinging to it, but not wet batter.
    Baking time may vary slightly depending on your oven, so watch carefully to avoid overbaking.
    The brownies should remain fudgy and slightly soft in the middle.
  • Cool Completely: Remove the pan from the oven and transfer it to a wire rack.
    Let the brownies cool completely in the pan before attempting to cut them.
    Cooling ensures the brownies firm up properly and the swirl sets, giving you clean, attractive squares.
    This may take 30–60 minutes, but patience here is key to achieving perfect texture.
  • Cut and Serve: Once cooled, use the parchment overhang to lift the entire brownie slab out of the pan.
    Place on a cutting board and cut into 16 equal squares with a sharp knife.
    For cleaner edges, wipe the knife with a warm, damp cloth between cuts.
    Serve immediately for the freshest, fudgiest experience.
    These brownies are perfect on their own, or paired with a scoop of ice cream or a glass of cold milk.
  • Storage Instructions: Store any leftover brownies in an airtight container at room temperature for up to one week.
    For longer storage, wrap tightly and freeze for up to three months.
    When ready to enjoy, let frozen brownies thaw at room temperature or warm gently in the microwave for a soft, gooey treat.

Notes

  • Use high-quality cocoa powder for the richest chocolate flavor. Dutch-processed cocoa gives a slightly smoother, less acidic taste, while natural cocoa offers a deeper chocolate intensity.
  • Avoid overmixing the brownie batter; folding just until combined keeps the texture fudgy and moist.
  • Let the brownies cool completely before cutting to ensure clean, sharp edges.
  • For a more pronounced peanut butter swirl, slightly heat the peanut butter mixture to make it more pourable.
  • You can swap creamy peanut butter with natural or chunky peanut butter, but adjust sweetness slightly if using unsweetened versions.
  • These brownies freeze well; wrap tightly in plastic wrap and then foil for best results.
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