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These Peanut Butter Swirl Brownies are the ultimate dessert for chocolate-peanut butter lovers! A double chocolate brownie batter is swirled with peanut butter fudge, and loaded with peanut butter cups. This recipe is perfect for holidays or a crowd!

Peanut Butter and chocolate is one of the best flavor combinations out there! Our super easy Chocolate Peanut Butter No Bake Cookies is our favorite way to enjoy chocolate & peanut butter without switching on the oven, and our Ultimate Butterfinger Brownies are the best, decadent indulgence!

two Peanut Butter Swirl Brownies stacked on top of each other

Easy Peanut Butter Brownies

We LOVE chocolate at our house. It’s just one of those things we can’t get enough of! Add some peanut butter and, oh my, we have definitely reached the next level of sweet perfection!

These Peanut Butter Swirl Brownies are incredibly decadent and worth every single bite. I started off with my Homemade Brownie Recipe (it’s seriously the best!) and then swirled in a modified version of my Old-Fashioned Easy Peanut Butter Fudge resulting in the fudgiest, gooey Peanut Butter Swirl Brownies you can dream of!

Square of Peanut Butter Swirl Brownies freshly cut on parchment paper, overhead shot

These delicious peanut butter brownies are so easy to whip up and ready in less than an hour. They smell AMAZING when they’re baking and it’s so difficult to not just cut right into them when they’re fresh out of the oven.

You can make them up to 4 or 5 days ahead of time (if you have that level of self-control!) making this Peanut Butter Swirl Brownie recipe perfect for a no-fuss dessert over the holidays, busy summers, for bake-offs or potlucks, or just anytime the craving strikes.

Close up of Peanut Butter Swirl Brownies
side shot of freshly cut Peanut Butter Swirl Brownies

Ingredients for Peanut Butter Brownies

  • Chocolate: Two kinds of chocolate are in this Peanut Butter Brownie recipe: Bittersweet chocolate is melted into the batter, and I added cocoa powder as well to give the brownies an extra chocolatey boost!
  • Sugar: We have 3 kinds of sugar in this recipe. Granulated sugar and brown sugar are both in the batter to add sweetness, keep the center gooey and the outside crisp. Powdered sugar is in our Peanut butter swirl as it’s easier to dissolve into the peanut butter than granulated sugar.
  • Vanilla extract: My Homemade Vanilla Extract brings out the best warm, sweet flavors in these brownies.
  • Peanut butter: Make sure to use creamy peanut butter like Skippy or Jif, and not natural peanut butter. The consistency just doesn’t do this recipe justice.
  • Butter: Butter is mixed into both the brownie batter and the peanut butter swirl, keeping these Peanut Butter Swirl Brownies ultra-moist.
  • Peanut butter cups: Any size will work because we’ll be chopping them up! Most of the peanut butter cups go into the batter but I like to reserve a handful to sprinkle on top.
Ingredients on marble background

How to Make the best Peanut Butter Swirl Brownies

  1. Prep the oven and baking dish. Preheat the oven to 350 degrees, and then line a square 9×9″ baking dish with a parchment paper sling or spray with baking spray.
  2. Melt chocolate and butter. Secondly, in a large microwave-safe bowl, combine the bittersweet chocolate and butter. Microwave on high in 20-30 second bursts, stirring well between bursts of heat until melted and smooth. Whisk in cocoa powder.
  3. Mix in sugar, eggs, and vanilla. Next, add the granulated sugar and brown sugar, whisking well to combine. Add the eggs and vanilla, beating well either by hand with a whisk or using an electric mixer.

4. Add in flour, salt, and peanut butter cups. After that, sprinkle the flour and salt over the brownie batter and gently stir it in with a wooden spoon or spatula, and then stir in most of the chopped peanut butter cups.
5. Make the Peanut Butter Swirl. In a separate bowl, make the peanut butter swirl by beating the melted butter, peanut butter, powdered sugar, and vanilla together until smooth.

Peanut butter fudge in bowl with mixer

6. Assemble. Drop about 2/3 of the brownie batter into the prepared pan by the spoonful. Fill in gaps with spoonfuls of the peanut butter mixture. Drop remaining brownie batter on top, then swirl both together with a knife.

7. Bake! Bake for 30 to 35 minutes, until a toothpick inserted into the center of the brownies, comes out mostly clean with only a few crumbs attached. Be sure not to overbake.

Peanut Butter Swirl Brownies freshly baked out of the oven in 9x9" pan

8. Cool, serve, and store. Finally, cool the Peanut Butter Swirl Brownies completely before cutting them. Store in an airtight container for up to 5 days on the counter or in the fridge.

Square of Peanut Butter Swirl Brownies freshly cut on parchment paper, overhead shot off center

Can I use a different size of pan?

Yes! I prefer the 9×9″ pan for brownies in general as it bakes evenly and quickly, however, an 8×8″ baking pan would work as well, giving you thicker brownies. You’d need to bake them for 10-15 more minutes with this pan.

Using a 9×13″ baking pan for Peanut Butter Swirl Brownies is also a good option! The brownies will be thinner and take 5-10 minutes less to cook.

How do I store Peanut Butter Swirl Brownies?

Store these delicious Peanut Butter Swirl Brownies in the fridge or on the counter in an airtight container for up to 5 days.

Individual slices of Peanut Butter Swirl Brownies on parchment paper, overhead shot

How long should I let brownies cool?

It’s difficult (the struggle is real!) but it’s best to let these Peanut Butter Swirl Brownies sit for about 30 minutes before cutting into them. But they cut better and actually have a more intense flavor when the brownies are allowed to cool before slicing into them.

What ingredient makes brownies fudgy?

The main reason these Peanut Butter Swirl Brownies are so fudgy is the butter! More fat content in a brownie means they will be softer and gooier, whereas cakey brownies have more flour in them.

Two Peanut Butter Swirl Brownies stacked on top of each other, bite missing from one brownie

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Peanut Butter Swirl Brownies
Yield: 12-16 brownies

Peanut Butter Swirl Brownies

These Peanut Butter Swirl Brownies are the ultimate dessert for chocolate-peanut butter lovers! A double chocolate brownie batter is swirled with peanut butter fudge, and loaded with peanut butter cups. This recipe is perfect for holidays or a crowd!

Prep Time 15 minutes
Cook Time 30 minutes
Total Time 45 minutes

Ingredients

Brownie Batter

  • 4 ounces bittersweet chocolate, chopped
  • 3/4 cup salted butter, cut into chunks
  • 1/2 cup unsweetened cocoa powder
  • 1 cup granulated sugar
  • 1/2 cup light brown sugar
  • 3 large eggs, room temperature
  • 2 teaspoons vanilla extract
  • 3/4 cup all-purpose flour
  • 1/2 teaspoon salt
  • 1 1/2 cups chopped peanut butter cups, reserving a handful to sprinkle on top

Peanut Butter Swirl

  • 3 tablespoons butter, melted
  • 3/4 cup creamy peanut butter (not the all-natural kind)
  • 1/3 cup powdered sugar
  • 1 teaspoon vanilla extract

Instructions

  1. Preheat oven to 350 degrees. Line a square 9x9" baking dish with a parchment paper sling or spray with baking spray.
  2. In a large microwave-safe bowl, combine the bittersweet chocolate and butter. Microwave on high in 20-30 second bursts, stirring well between bursts of heat until melted and smooth. Whisk in cocoa powder.
  3. Add granulated sugar and brown sugar, whisking well to combine. Add eggs and vanilla, beating well either by hand with a whisk or using an electric mixer.
  4. Sprinkle the flour and salt over the brownie batter and gently stir it in with a wooden spoon or spatula. Stir in most of the chopped peanut butter cups.
  5. In a separate bowl, make the peanut butter swirl by beating the melted butter, peanut butter, powdered sugar, and vanilla together until smooth.
  6. Drop about 2/3 of the brownie batter into the prepared pan by spoonfuls. Fill in gaps with spoonfuls of the peanut butter mixture. Drop remaining brownie batter on top, then swirl both together with a knife.
  7. Bake for 30 to 35 minutes, until a toothpick inserted into the center of the brownies comes out mostly clean with only a few crumbs attached. Be sure not to overbake.
  8. Cool completely before cutting. Store in an airtight container for up to 5 days on the counter or in the fridge.

Notes

  • 8x8-inch baking pan: These will be thicker and take longer to bake, more like 40-45 minutes.
  • 9x13-inch baking pan: This recipe can be spread into a larger pan and baked thinner for 20-25 minutes.