Peanut Butter Brownies (Easy + Fudgy!)
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Peanut Butter Brownies (Easy + Fudgy!)
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COOK TIME
40 min
TOTAL TIME
50 min + chill time
SERVINGS
10-12 servings
These Peanut Butter Brownies taste like a giant homemade peanut butter cup with layers of fudgy brownies, creamy peanut butter, and rich chocolate frosting. They start with a simple box brownie mix, which makes them incredibly easy while still tasting completely homemade!
Reese’s Peanut Butter Cups have always been my weakness. My daughter fully knows this and automatically hands them over after Halloween like some sort of tiny candy tax collector. Peanut butter and chocolate is just one of those classic combinations that never gets old and I will never stop loving it no matter how old I get!
These brownies actually happened because I made my Marshmallow Brownies for a friend and as I do, I immediately started thinking about other versions I could make. I’m a big fan of desserts that feel homemade without actually making me dirty every bowl in the kitchen. So yes, I happily use a boxed brownie mix here and honestly I think Ghirardelli brownies are hard to beat anyway.
I swapped the marshmallow layer for creamy peanut butter and changed the frosting so it sets into that soft chocolate shell texture that cracks a little when you bite into it, just like a peanut butter cup. The layers together are ridiculously good. Rich brownies, creamy peanut butter, chocolate frosting, and absolutely zero self control around the pan for me and anyone who comes in contact with them!
Why You’ll Love These Brownies with Peanut Butter
They use a boxed brownie mix, which keeps the recipe simple and cuts down on prep time.
The peanut butter layer stays soft and creamy against the rich brownie base, giving every bite a rich peanut butter cup flavor.
The homemade chocolate frosting sets into a thick fudgy layer that makes these brownies feel more homemade than a typical boxed brownie recipe.
You can make them in either an 8×8 pan for thick bakery-style brownies or a 9×13 pan if you want thinner brownies for a larger group.
They store well in the refrigerator, making them easy to prepare ahead for parties, bake sales, or holidays.
Ingredients You’ll Need
Boxed Brownie Mix – The base of the recipe and the reason these brownies come together so easily. I usually grab the Ghirardelli mix because it bakes up extra fudgy and holds the peanut butter and frosting layers really well.
Creamy Peanut Butter – Creates the thick middle layer that gives these brownies a peanut butter cup flavor. Regular creamy peanut butter spreads the easiest and sets up best after chilling.
For The Frosting
Butter – Melted butter gives the frosting a rich texture and helps everything come together smoothly in the saucepan.
Large Marshmallows – The marshmallows melt into the frosting and help create that soft chocolate shell texture once chilled. It ends up somewhere between frosting and candy in the best possible way. It sounds a little random at first but it works so well here!
Powdered Sugar – Sweetens the frosting while also helping it thicken into a spreadable layer that firms up in the refrigerator.
Milk – Helps loosen the frosting just enough so it spreads easily over the peanut butter layer before setting.
Unsweetened Cocoa Powder – Adds deep chocolate flavor to balance the sweetness from the marshmallows and powdered sugar.
How To Make Peanut Butter Cup Brownies
Prepare for baking: Preheat the oven according to the brownie mix package directions. Line an 8×8 baking dish with parchment paper for thicker brownies and more defined layers, or use a 9×13 baking dish if you want thinner brownies. Lightly spray the parchment paper or baking dish with nonstick cooking spray.
Bake the brownies: Prepare the boxed brownie mix according to the package instructions and pour the batter into the prepared baking dish. Bake until the brownies are set in the center and a toothpick comes out with just a few moist crumbs. Let the brownies cool completely before adding the peanut butter layer so the layers stay separate and clean.
Soften the peanut butter layer: Add the creamy peanut butter to a microwave safe bowl and heat for 15-30 seconds until softened and easy to stir. The peanut butter should be loose enough to spread easily without being hot or oily. Pour the peanut butter over the cooled brownies and use an offset spatula or the back of a spoon to spread it into an even layer all the way to the edges.
Chill the brownies: Transfer the brownies to the freezer for 20-30 minutes so the peanut butter layer can firm up before adding the frosting. This helps keep the layers neat and prevents the warm frosting from mixing into the peanut butter.
Make the chocolate frosting: In a medium saucepan over medium heat, melt the butter and marshmallows together, stirring frequently until smooth. Reduce the heat to low and whisk in the powdered sugar, milk, and cocoa powder until the frosting is thick, smooth, and fully combined with no dry spots remaining.
Add the frosting layer: Remove the brownies from the freezer and immediately pour the warm chocolate frosting over the peanut butter layer. Spread the frosting evenly across the top while it is still warm since it begins to set as it cools.
Chill and slice: Return the brownies to the freezer for another 20-30 minutes until the frosting is set. Once chilled, lift the brownies out of the pan using the parchment paper and cut into squares using a sharp knife. Store the brownies in the refrigerator until ready to serve. Enjoy!
Expert Tips
Let the brownies cool longer than you think you need to. Even slightly warm brownies can melt the peanut butter layer and make the layers slide around when slicing. I usually give them at least an hour on the counter before moving on.
Warm the peanut butter in short bursts. Peanut butter goes from perfectly spreadable to oily surprisingly fast in the microwave. Fifteen second intervals work much better than one long heating session.
Use an offset spatula if you have one. It makes spreading the peanut butter and frosting layers much easier without dragging crumbs up into the top layer.
Whisk the frosting constantly once the powdered sugar goes in. The marshmallow mixture thickens quickly.
Cut the brownies straight from the refrigerator. Cold brownies slice much cleaner and keep those peanut butter and chocolate layers looking neat.
Wipe the knife clean between slices. The peanut butter layer sticks to the knife pretty quickly, especially after a few cuts. A clean knife makes the brownies look much more polished.
Ways To Customize
Swap the creamy peanut butter for crunchy peanut butter if you want a little texture in the middle layer.
Use dark chocolate brownie mix for a richer chocolate flavor.
Add chopped Reese’s Peanut Butter Cups over the frosting before chilling for extra peanut butter and chocolate.
Replace the peanut butter with almond butter or cookie butter for a completely different flavor while.
Sprinkle flaky sea salt over the frosting before it sets to balance the sweetness and make the chocolate flavor pop more.
Add mini chocolate chips between the brownie and peanut butter layers.
Mix espresso powder into the frosting to deepen the chocolate flavor without making the brownies taste like coffee.
Storing & Freezing
Storing: Store the peanut butter brownies covered in the refrigerator for up to 5 days. I usually keep them in the pan tightly wrapped with plastic wrap or transfer slices to an airtight container once they’re cut. The chilled texture keeps the peanut butter and frosting layers firm.
Freezing: These brownies freeze really well once the layers are fully set. Cut them into squares first, then place them in a freezer-safe container in one layer so they do not stick together. Freeze for up to 2 months and thaw the brownies in the refrigerator for a few hours before serving. They are also surprisingly good partially frozen straight from the freezer!
FAQ
Can I use crunchy peanut butter instead of creamy peanut butter?
Yes! Crunchy peanut butter adds texture to the middle layer and gives the brownies a little more of a candy bar feel once chilled.
Why does the peanut butter layer need to chill before adding the frosting?
The warm frosting spreads much more cleanly over cold peanut butter. Chilling also keeps the layers from blending together while you spread the frosting on top.
What is the easiest way to cut clean brownie squares?
Chill the brownies completely before slicing and wipe the knife clean between each cut. A plastic knife actually works well for getting neat slices without dragging the frosting.
Can I use homemade brownies instead of boxed brownie mix?
Absolutely! Homemade brownies work great here, especially dense fudgy brownies that can support the peanut butter and frosting layers without falling apart.
More Brownie Recipes
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Peanut Butter Brownies
These Peanut Butter Brownies taste like a giant homemade peanut butter cup with layers of fudgy brownies, creamy peanut butter, and rich chocolate frosting. They start with a simple box brownie mix, which makes them incredibly easy while still tasting completely homemade!
Ingredients
Brownie Layer
Box Brownie Mix (I love the Ghiradelli Brand) or I love these Easy Homemade Brownies
Peanut Butter Layer
One 16oz jar creamy peanut butter
Fudgy Frosting
8 tablespoons (1 stick) unsalted butter
10 large marshmallows
4 cups powdered sugar
1/3 cup whole milk
1/4 cup unsweetened cocoa powder
Instructions
1. Prepare for baking: Preheat the oven according to the brownie mix package directions. Line an 8×8 baking dish with parchment paper for thicker brownies and more defined layers, or use a 9×13 baking dish if you want thinner brownies. Lightly spray the parchment paper or baking dish with nonstick cooking spray.
2. Bake the brownies: Prepare the boxed brownie mix according to the package instructions and pour the batter into the prepared baking dish. Bake until the brownies are set in the center and a toothpick comes out with just a few moist crumbs. Let the brownies cool completely before adding the peanut butter layer so the layers stay separate and clean.
3. Soften the peanut butter layer: Add the 16oz jar of creamy peanut butter to a microwave safe bowl and heat for 15-30 seconds until softened and easy to stir. The peanut butter should be loose enough to spread easily without being hot or oily. Pour the peanut butter over the cooled brownies and use an offset spatula or the back of a spoon to spread it into an even layer all the way to the edges.
4. Chill the brownies: Transfer the brownies to the freezer for 20-30 minutes so the peanut butter layer can firm up before adding the frosting. This helps keep the layers neat and prevents the warm frosting from mixing into the peanut butter.
5. Make the chocolate frosting: In a medium saucepan over medium heat, melt the 1 stick of butter and 10 marshmallows together, stirring frequently until smooth. Reduce the heat to low and whisk in the 4 cups powdered sugar, 1/3 cup milk, and 1/4 cup cocoa powder until the frosting is thick, smooth, and fully combined with no dry spots remaining.
6. Add the frosting layer: Remove the brownies from the freezer and immediately pour the warm chocolate frosting over the peanut butter layer. Spread the frosting evenly across the top while it is still warm since it begins to set as it cools.
7. Chill and slice: Return the brownies to the freezer for another 20-30 minutes until the frosting is set. Once chilled, lift the brownies out of the pan using the parchment paper and cut into squares using a sharp knife. Store the brownies in the refrigerator until ready to serve. Enjoy!
Notes
-
Let the brownies cool longer than you think you need to. Even slightly warm brownies can melt the peanut butter layer and make the layers slide around when slicing. I usually give them at least an hour on the counter before moving on.
-
Warm the peanut butter in short bursts. Peanut butter goes from perfectly spreadable to oily surprisingly fast in the microwave. Fifteen second intervals work much better than one long heating session.
-
Cut the brownies straight from the refrigerator. Cold brownies slice much cleaner and keep those peanut butter and chocolate layers looking neat.
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