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stack of 3 peanut butter swirl brownies

It’s no secret that I love using peanut butter in my baking. Peanut butter cookies and no-bake peanut butter bars are on repeat in my kitchen. But can you believe I’ve never shared a peanut butter swirl brownie recipe on my website before?

Actually, wait. I did share skinny peanut butter swirl brownies about 5 years ago that’s made with zero flour, a blender, Greek yogurt, and oats. Sounds very strange, but it totally works. By the way, I’ve since made them with coconut sugar and they’re SO GOOD. I’ve also made peanut butter filled brownie cookies!

peanut butter swirl brownies cut into squares

We’re not on a diet today. This is the real deal. The obnoxiously fudgy dense brownies completely overloaded with chocolate and swirled with an awesomely rich peanut butter filling and– wait for it– filled with chopped peanut butter cups. If you listen closely, you can hear your bikini running away in fright.

I label them “mega” because they’re one of the richest desserts to come out of my oven. The base of the brownies is this homemade brownies recipe, though I add a little more chocolate. If you’ve tried that brownie recipe before, you can imagine how “mega” the peanut butter swirl version is!

I made the first batch of mega peanut butter swirl brownies nearly a month ago when our friends came to visit. I knew neither Kevin nor I could be trusted with an entire batch just to ourselves and I’m going to warn you now– make sure you’ve got company coming over or a large group to help you snack on these! Self control seems to run for the hills. Maybe it’s hanging out with our bikinis.

So here’s how we’re going to make them…

brownie batter in a glass bowl with chopped peanut butter cups

Whip up the homemade brownie batter. That’s easy. Curious about the ingredients and why each is important? You can review my homemade brownies post for more.

Add chopped peanut butter cups. ♥ And if you love them in these brownies, you’ll love them in my peanut butter cup crunch brownies, too!

Prepare the epic PB swirl next. There’s a lot of it because we want mega peanut butter swirls in every single bite. Clearly, we’re not skimping on anything today.

Only 4 ingredients needed for the peanut butter swirl: creamy peanut butter, confectioners’ sugar, butter, and vanilla extract– pretty much the same ingredients we use for peanut butter balls and peanut butter eggs, too. You’re using butter and vanilla in the brownie recipe anyway, so really it’s just 2 additional ingredients. The easiest way to combine them all is using a mixer.

peanut butter swirl mixture in a glass bowl with a hand mixer

How to Perfect the Swirl

Since we’re making a super mega dessert, we want to make sure it looks pretty darn good too. The swirling part is an art, but one you can easily master on the first try. All you do is randomly drop spoonfuls of brownie batter and spoonfuls of peanut butter batter into the lined brownie pan. It’s going to be super haphazard like so:

scoops of brownie batter and peanut butter swirl mixture in a baking pan lined with parchment paper

Save a couple spoonfuls of brownie batter to fill in any gaps or cover any heavy peanut butter sections. Then take a knife and run it up and down both horizontally and vertically, creating swirls of the two batters like so:

peanut butter mixture and brownie batter swirled together in a baking pan

Easy stuff, right? Sprinkle the pan with a couple leftover chopped peanut butter cups and pop into the oven.

This brownie recipe, without the peanut butter swirl, takes about 30-32 minutes. The peanut butter swirl adds a couple minutes to the bake time. But I urge you to watch the brownies themselves– not the clock. The bake time is simply a guideline and you shouldn’t be surprised or alarmed if the brownies take longer or shorter. You’ll know the brownies are done when the top looks set. Test them using a toothpick. If there is wet batter on the toothpick, the brownies need more time. If there are a few moist crumbs on the toothpick, the brownies are done. If the toothpick is clean, the brownies are overdone. So keep your eyes on these!

overhead image of peanut butter swirl brownies

How to Neatly Cut Brownies

Another art you can master on the first try!

  1. Wait until the brownies have completely cooled. What a buzzkill. But this helps ensure some neatly sliced fudgy brownies! I always stick the slightly cooled pan in the fridge for an hour or so to speed up the process.
  2. Use a plastic knife. One of those dinky ones you buy for potlucks and picnics. SO WEIRD, right? But a plastic knife strangely keeps layered or swirled brownies neat. It’s my little trick for neatly cut mint chocolate brownies. If you don’t have one and really don’t feel like getting one, just use a very sharp knife.
  3. Whichever knife you use, wipe it clean with a paper towel between each cut.

That’s all, folks!

peanut butter swirl brownie

My last piece of advice: have a mega glass of milk handy. Or at least some sweatpants.

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peanut butter swirl brownie

Mega Peanut Butter Swirl Brownies

  • Author: Sally
  • Prep Time: 20 minutes
  • Cook Time: 35 minutes
  • Total Time: 3 hours, 20 minutes
  • Yield: 1824 brownies 1x
  • Category: Brownies
  • Method: Baking
  • Cuisine: American


These mega peanut butter swirl brownies are unapologetically rich and fudgy! This homemade brownie recipe is one of my favorites and so easy to make.


  • 1 cup (16 Tbsp; 2 sticks; 230g) unsalted butter, divided
  • one 4 ounce (113g) semi-sweet chocolate bar, coarsely chopped*
  • 2 cups (400g) granulated sugar
  • 3 large eggs, at room temperature
  • 2 teaspoons pure vanilla extract, divided
  • 1 cup (82g) unsweetened natural or dutch-process cocoa powder*
  • 1 cup (125g) all-purpose flour (spoon & leveled)
  • 1 teaspoon salt
  • 1 and 1/2 cups chopped peanut butter cups
  • 1 cup (250g) creamy peanut butter*
  • 1/2 cup (60g) confectioners’ sugar


  1. Preheat the oven to 350°F (177°C) and grease a 9×13 inch pan or line with aluminum foil or parchment paper, leaving an overhang on the sides to lift the finished brownies out (makes cutting easier!). Set aside.
  2. Brownie batter: In a microwave-safe bowl, combine 3/4 cup butter (12 Tbsp; 1 and 1/2 sticks) and chopped chocolate. Melt in 30 second increments, whisking after each, until completely smooth. Whisk in the granulated sugar until completely combined, then whisk in the eggs and 1 teaspoon vanilla. The batter will be light brown and a little dull looking.
  3. Add the cocoa powder, flour, and salt. Fold it all together with a rubber spatula or wooden spoon. Batter will be very thick. Stir in chopped peanut butter cups, reserving a small handful to sprinkle on top. Set aside.
  4. Peanut butter swirl: Melt the remaining butter. Using a hand-held or stand mixer fitted with a paddle or whisk attachment, beat the melted butter, remaining 1 teaspoon of vanilla, the peanut butter, and confectioners’ sugar until smooth. Drop big spoonfuls of most of the chocolate batter randomly into the prepared pan– see photo above for a visual. Top with random spoonfuls of all of the peanut butter batter. Drop random spoonfuls of remaining chocolate batter over any bare spots or heavy peanut butter spots. Using a knife, swirl the batters together. The brownie batter is pretty thick, so do your best. Sprinkle with any leftover peanut butter cups.
  5. (See note about how to tell if brownies are done in the post above.) Bake for 30 minutes, then test the brownies with a toothpick. Insert it into the center of the pan. If it comes out with wet batter, the brownies are not done. If there are only a few moist crumbs, the brownies are done. Keep checking every 2 minutes until you have moist crumbs. My brownies take 33-36 minutes.
  6. Remove from the oven and place on a wire rack to cool completely before cutting into squares. Cover and store leftover brownies at room temperature for up to 1 week.


  1. Make Ahead Instructions: Brownies freeze well up to 3 months. Thaw overnight in the refrigerator then bring to room temperature before serving.
  2. Chocolate Bars: Chocolate bars are typically sold in 4 ounce bars. I suggest Ghirardelli, Baker’s brand, or Lindt. Do not use chocolate chips.
  3. Cocoa Powder: You can use either natural or dutch-process cocoa powder. I prefer dutch-process for a smoother flavor.
  4. Peanut Butter:Use a generic creamy peanut butter like Jif or Skippy. Crunchy could work too. Do not use natural, homemade, or super oily brand as the swirl will not set up properly.

Keywords: peanut butter swirl brownies

Here’s that older recipe for the skinny version!

stack of 2 peanut butter chocolate brownies

Reader Questions and Reviews

  1. Instead of semi sweet chocolate bar, could I use cocoa powder substitute? Thanks!

  2. Could this be doubled and baked in a sheet pan? Just asking as I need double the amount of servings.
    As always, thanks.

    1. Hi Sheila, We haven’t tested that large of a pan of brownies before! You can certainly try it but I fear they may not bake very evenly in such a big pan. It may be best to simply bake this recipe twice but let us know if you give it a try!

  3. I have made the brownies many times, with no problems. Today, I tried these. Sorry, never again. The PB swirl was really thin. Took almost an hour to bake. They have been cooling for hours and the swirl still hasn’t set.
    I’ll go back to the original recipe.
    Yes, everything was measured.

  4. Made these for a family member’s birthday who loves PB & choc and he absolutely loved them! I will say that like some other commenters I had some issues getting the peanut butter swirl to firm up and it did take a while, probably about twice the recipe’s bake time. I ended up tenting the edges with foil and turning the oven temp down a bit but probably could have done that even earlier to help it bake more evenly. Also some of the more liquidy bits of PB ended up solidifying during cooling so I likely could have cut the baking time down a touch. Final result was a bit crumbly in places, but still tasty. If you’re looking for top tier presentation/clean cut bars this may not be the recipe for you, but if taste is what you’re after these certainly do the job.

  5. Another fantasic recipe. Sally is excellent at clearly laying out the ingredients and the steps to take. My dog got to lick the peanut butter bowl (just a little bit).

  6. I’m not sure where I went wrong, my peanut butter also did not set and separated from the batter. And I felt it was too salty I would maybe omit salt from it as you get it from the PB.

  7. I followed this exactly and am really disappointed. Consistency of the peanut butter portion was too thin and the finished product is visually unappealing.

  8. I am pretty savvy when it comes to baking, but this recipe was a big fail for me. I measured everything correctly, used the recommended products, and followed the notes/steps exactly. I even checked the comments to see any other suggestions. I had to call it at an hour even though it wasn’t anywhere near set. The peanut butter portion was crumbly and dry, and the brownie portion was a little underdone. I think I’ll stick with her other fabulous brownie recipes that have been hits. Her recipes, with the exception of this one, are in regular rotation and always succeed.