There are desserts that hit the spot when you’re craving something sweet, and then there are desserts that stop you in your tracks because they’re just that good. These Gooey Peanut Butter Brownies fall squarely into the second category. They’re fudgy, rich, and unapologetically indulgent—the kind of treat that makes you sneak back into the kitchen for “just one more bite.”
This recipe is one that reminds me of cozy afternoons when the oven warms up the whole kitchen, and everyone magically wanders in to see what’s baking. The smell of chocolate brownies mixed with sweet marshmallow and peanut butter is pure comfort. And let’s be real—peanut butter and chocolate are one of those timeless flavor pairings that never disappoint. Add marshmallow crème into the mix, and you’ve got a dessert that’s gooey, nostalgic, and a little bit over-the-top in the best way.
Whether you’re making these for a bake sale, a family gathering, or just because you want something ridiculously good after dinner, this recipe will deliver every single time.
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Why You’ll Love These Gooey Peanut Butter Brownies
It’s outrageously gooey.
The sweetened condensed milk and marshmallow crème create a soft, creamy center that stays fudgy long after baking. These bars are rich in the best possible way.
You get layers of flavor.
Deep chocolate brownie base. Sweet marshmallow swirl. Melty peanut butter morsels. Every bite tastes like something special — not just “another brownie.”
It starts with a simple brownie mix.
No complicated steps. No fancy techniques. You get bakery-style results without the stress.
That crackly top is irresistible.
As they bake, the top turns beautifully shiny and slightly crackled — the kind of texture that makes people reach for seconds.
Perfect for sharing.
These are ideal for holidays, potlucks, bake sales, or family gatherings. Cut them small and watch them disappear.
They taste nostalgic.
There’s something about marshmallow and peanut butter together that feels classic and comforting — like a childhood favorite, just upgraded.
Make-ahead friendly.
They actually slice better the next day, which makes them perfect for prepping in advance.
Ingredient Breakdown
Here’s what you’ll need to make these irresistible brownies:
- Sweetened Condensed Milk – Adds richness, sweetness, and that gooey texture we’re after.
- Butter (melted & cooled) – Gives the brownies a rich, buttery depth.
- Milk – Helps loosen up the batter since it’s extra thick with the mix-ins.
- Brownie Mix – Any standard box of brownie mix works here. Choose your favorite brand.
- Egg – Just one, lightly beaten egg white, to help bind everything together.
- Marshmallow Crème – For that sticky-sweet gooey layer in the middle.
- Peanut Butter Morsels – For the ultimate peanut butter taste.
- Cooking Spray – Essential for making sure these rich brownies don’t stick to the pan.
Instructions
- Step 1: Mix brownie mixture together.
- Step 2: Read “Special Instructions” Section on how to prep pan. Press ⅔ of mixture into a well greased pan (and parchment paper), bake for 10 minutes at 350 degrees.
- Step 3: Mix sweetened condensed milk with marshmallow fluff and peanut butter chips.
- Step 4: Pour marshmallow mixture on top of par baked brownie. Then top with dollops of remaining brownie mixture and bake for 30-40 minutes at 350 degrees.
Step-by-Step Tips for Success
Mix with a stand mixer: The batter will be very thick (thanks to the condensed milk), so don’t worry if it feels heavier than a normal brownie batter. That’s exactly how it should be.
Spray your spatula: When spreading the brownie mixture into the pan, lightly spray your spatula with cooking spray. It prevents sticking and makes spreading much easier.
Partial bake is key: That first 10-minute bake helps set the base layer so the marshmallow mixture doesn’t sink straight into the batter.
Don’t worry about perfection: When you drop the remaining brownie batter over the marshmallow layer, it won’t cover evenly—and that’s the beauty of it. The gooey swirls on top are what make these brownies so irresistible.
Variations
- Nutty Crunch: Add a handful of chopped peanuts or walnuts into the top layer before baking for extra crunch.
- Extra Chocolatey: Drizzle melted chocolate chips along with the peanut butter for a double-swirled effect.
- Peanut-Free Option: Swap peanut butter morsels for butterscotch or caramel chips.
- Holiday Twist: Mix in festive sprinkles or colored candy-coated chocolates for a fun seasonal version.
Serving Suggestions
- Pair with a tall glass of cold milk—classic and unbeatable.
- Warm a square in the microwave for 10–15 seconds and top with a scoop of vanilla ice cream.
- Slice into smaller bites and serve on a dessert tray at parties.
- Enjoy them straight from the pan while standing in the kitchen (no judgment).
Storage & Make-Ahead
- Room Temperature: Store in an airtight container for up to 3 days.
- Refrigerator: Keep up to 1 week if you like a firmer, fudgier texture.
- Freezer: Wrap individual brownie squares in plastic wrap and store in a freezer bag for up to 3 months. Thaw at room temperature or microwave for a quick treat.
Frequently Asked Questions
Q: Can I use a homemade brownie recipe instead of a box mix?
A: Absolutely! Just make sure it’s for a 9X9-inch pan so the proportions stay balanced.
Q: Do I have to use marshmallow crème?
A: It’s what makes these gooey! But if you prefer, you could substitute mini marshmallows (though the texture will be a little different).
Q: Can I double this recipe?
A: Yes, but you’ll need two pans. A single batch already fills a 9X9-inch dish nicely.
Q: How do I know when they’re done?
A: The edges will look set, and the top will have a slightly crackly texture. The center may still look soft—that’s okay, they’ll firm up as they cool.
Absolutely — here’s a clear, polished section written in your warm, instructional tone:
Special Instructions: How to Prepare the Pan
Proper pan prep makes all the difference with these ultra-gooey brownie bars. Don’t skip this step — it ensures clean removal and easy slicing later.
Step 1: Spray the pan first.
Lightly coat your 9×9-inch baking dish with non-stick cooking spray. This first layer helps the parchment paper adhere to the pan so it doesn’t shift while you spread the thick batter.
Step 2: Line with parchment paper.
Place parchment paper into the pan, leaving enough overhang on two opposite sides. This creates “handles” so you can lift the brownies out easily after they cool.
Press the parchment into the corners so it sits flat against the bottom and sides.
Step 3: Spray again.
Lightly spray the parchment paper with non-stick cooking spray as well. This second spray ensures the brownies release cleanly — especially important since this recipe is rich and gooey.
This double-spray method prevents sticking, makes cleanup easier, and gives you those beautiful, clean-edged squares when it’s time to slice.
Why This Recipe Works
These Gooey Peanut Butter Brownies are built on the foundation of a fudgy boxed brownie mix, but it’s the add-ins that transform them. The sweetened condensed milk makes the brownies extra moist and dense, the marshmallow crème gives them that gooey pull-apart factor, and the peanut butter swirl ties everything together with a salty-sweet kick. It’s an easy recipe, but one that feels special and bakery-worthy without the fuss.
Final Thoughts
These Gooey Marshmallow Peanut Butter Brownie Bars are the kind of dessert that makes people pause after the first bite. They’re rich. They’re soft. They’re unapologetically indulgent.
The crackly top gives way to that creamy marshmallow layer and melty peanut butter pockets underneath — and somehow every bite tastes even better than the last. This isn’t a “grab one and move on” kind of brownie. It’s a “cut a smaller square… then come back for another” kind of treat.
What I love most is how simple they are to make. A boxed brownie mix turns into something that feels completely homemade and bakery-worthy. No complicated techniques. No fussy steps. Just layered goodness that delivers every time.
They’re perfect for holidays, potlucks, game days, or those evenings when you just want something extra comforting and chocolatey. And honestly? They might taste even better the next day.
If you make them, slice them small… serve them proudly… and don’t be surprised when someone asks for the recipe before they even finish their first piece. These are the kind of bars that become a repeat request.
Love Brownies? Try out some of my favorite chocolate desserts:
Peppermint Hot Chocolate Brownies
Gooey Peanut Butter Brownies
Ingredients
Equipment
Method
- In stand mixer, combine ¼ cup of the sweetened condensed milk, melted butter, milk, brownie mix and egg white. The batter will be thick.
- Use Parchment paper AND no stick spray (spray Non-stick spray on top of the parchment paper) to prepare the 9×9-inch baking dish. Spread ⅔ of the brownie batter into the bottom of the pan (it helps to use a spatula sprayed with cooking spray). The layer will be thin.
Bake the base: Bake for 10 minutes at 350°F.
- In a medium bowl, stir together the remaining ½ cup sweetened condensed milk with the marshmallow crème and peanut butter morsels. Mix until smooth.
- Spread the marshmallow mixture evenly over the partially baked brownie layer. Carefully drop the remaining brownie batter by spoonfuls over the marshmallow layer. ( try to spread out the brownie batter at much possible)
- Optional step: swirl the top layer for a nicer look, being careful not to swirl the bottom layer.
Final bake: Return to the oven and bake for 35-45 minutes at 350°F, until the top looks set and slightly crackly.
- Let cool completely before cutting into squares. These are rich and gooey, so smaller portions work best!
Notes
This is normal! The sweetened condensed milk makes the brownie layer dense and rich. Spread gently with a spatula sprayed with cooking spray to prevent sticking. • Use parchment paper for best results.
Lining your 9×9 pan makes removal much easier. These bars are gooey and can stick if you skip this step. • Don’t overbake.
The top should look set and slightly crackly. The center may still have a slight jiggle — it will firm up as it cools. • Cooling is key.
Let the bars cool completely before slicing. For cleaner cuts, refrigerate for 30–60 minutes before cutting into squares.
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