Fudgy Peanut Butter Marshmallow Swirl Brownies
Add these peanut butter marshmallow brownies to your list of indulgent treats!
- Prep
- 20 mins
- Cook
- 32 mins
- Total
- 52 mins
- Makes
- 24 servings
Get ready for a decadent treat with these Marshmallow Peanut Butter Brownies. They pair rich, chewy chocolate brownies with marshmallow fluff and a peanut butter filling swirled across the top! The recipe comes from my friend Sarah Kieffer's new cookbook, 100 Cookies, and it's perfect for any brownie lover in your life!
6 Reasons You'll Want to Bake These
- Rich, chocolatey brownies that land somewhere between fudgy and cakey, the best of both worlds!
- You don't need a hand mixer or a stand mixer.
- Peanut butter and marshmallows swirled right on top!
- Quick to prepare and bakes in about 26-32 minutes.
- Chocolate, peanut butter, and marshmallow make a heavenly trio of flavors!
- They come from Sarah Kieffer's new cookbook, 100 Cookies!
About the Author: Sarah Kieffer
Sarah is a true expert when it comes to cookies and brownies! She's best known for her pan-banging cookies, which get an entire chapter in her latest book, 100 Cookies.
She also revives her well-loved "My Favorite Brownies" recipe from her first book, The Vanilla Bean Baking Book. That's the base recipe I used for these marshmallow peanut butter brownies.
If you love brownies and cookies (or really any dessert), I highly recommend picking up both of her cookbooks, reading her blog, The Vanilla Bean Blog: A Baker's Soliloquy, or following her on Instagram!
On a personal note, Sarah is one of the coolest and kindest people I've met in the baking blog world. I'm so proud of her and everything she has accomplished!
Baking Tools Needed
These are the baking tools I suggest for making these marshmallow peanut butter brownies.
- 9 x 13-inch baking pan. My Nordic Ware metal pan is my favorite for sheet cakes, rice krispie treats, and these brownies!
- Baker's Joy Baking Spray. This is my go-to for greasing any baking pan. A light coating of butter dusted with flour, or vegetable shortening dusted with flour, works in its place.
- Parchment paper. Optional, but it really makes it easier to lift the brownies out so they can cool and be cut.
- Mixing bowls. You'll need at least 3 for this recipe. Two small ones and a medium one works well.
- Saucepan. Use this to melt the chocolate and butter together. I used my Dansk 1 quart hot cocoa pot.
- Whisks and spatulas. Whisks are great for combining the dry and wet ingredients. A spatula is the better choice for bringing the two together and for pouring the batter into the pan.
- Wire cooling rack. For letting the marshmallow peanut butter brownies cool.
- Large knife. A big, sharp knife always comes in handy for cutting brownies!
How to Make These
Here is a general overview of making these marshmallow peanut butter brownies with a peanut butter filling and marshmallow fluff. The full recipe is below, and you can also find it in Sarah's 100 Cookies cookbook!
Make the peanut butter filling. This is easy to do in a small bowl with a whisk or spatula. I like to start with it before making the brownies. You'll need creamy peanut butter, confectioners' sugar, unsalted butter, and salt.
Whisk the dry ingredients together. Combine the all-purpose flour, salt, and baking powder.
Whisk the wet ingredients. Use a separate bowl for this. Combine the eggs, canola oil, granulated and brown sugars, and vanilla extract.
Melt the butter and chocolate. Chop the chocolate into small pieces or break it into smaller chunks, then melt it in a small, heavy-bottomed saucepan. Stir this into the wet ingredients until well blended.
Add the dry ingredients to the wet. Mix until just combined.
Pour the brownie batter into the prepared pan. Use your spatula to scrape every last bit of batter out of the bowl.
Dollop, then swirl. Take turns dolloping the peanut butter filling and marshmallow fluff over the batter. Then gently swirl everything together with a butter knife.
Bake, then cool. These marshmallow peanut butter brownies need 26-32 minutes at 350ºF. Let them cool on a wire rack afterward, and make sure they're completely cool before cutting.
Frequently Asked Questions
Can I use the microwave to heat the chocolate and butter?Yes! Heat for 45 – 60 seconds on medium power. Stir, then repeat until both ingredients have fully melted and are smooth. Stir in the cocoa powder afterward.
Will these brownies keep at room temperature?Yes! They keep for up to 2 days in a sealed food container. They'll also last a day or two longer in the refrigerator.
My Top Brownie-Making Tips
Use the parchment sling. It makes lifting the brownies out of the pan to cool easier, and cutting them is a breeze!
Mix up the peanut butter filling first. This is a small time-saver. Once the brownie batter is in the pan, you'll want to dollop on the peanut butter filling and marshmallow fluff right away.
Warm up the marshmallow fluff. Microwaving it for 15 seconds made it much easier to dollop onto the brownies.
Swirling 101. Just skim the top of the brownies as you swirl. I got a little carried away and pushed most of the marshmallow fluff down inside. They still tasted incredible, and it was fun to see the marshmallow peeking through with each bite. They just aren't as pretty as Sarah's!
Need More Brownies in Your Life?
Fudgy Peanut Butter Marshmallow Swirl Brownies
These Marshmallow Peanut Butter Brownies are a must for your list of indulgent treats! They pair rich, chewy chocolate brownies with marshmallow fluff and a peanut butter filling swirled across the top! The recipe comes from my friend Sarah Kieffer's new cookbook, 100 Cookies, and it's perfect for any brownie lover in your life!
- Prep
- 20 mins
- Cook
- 32 mins
- Total
- 52 mins
- Makes
- 24 servings
Ingredients
peanut butter filling
- 1/2 cup Creamy Peanut Butter
- 1/4 cup Powdered Sugar
- 2 tbsp Unsalted Butter, room temperature
- Pinch of Salt
brownies
- 1 cup + 2 tbsp All-Purpose Flour
- 3/4 tsp Salt
- 1/2 tsp Baking Powder
- 4 Large Eggs, room temperature
- 1 1/2 cups Granulated Sugar
- 1/2 cup Brown Sugar, packed
- 1/2 cup Canola Oil
- 2 tsp Pure Vanilla Extract
- 8 tbsp Unsalted Butter
- 8 oz Bittersweet Chocolate, chopped
- 1/4 cup Dutch Process Cocoa Powder
- 1/2 cup Store-Bought Marshmallow Fluff
Method
- In a medium bowl, mix the peanut butter, powdered sugar, unsalted butter, vanilla, and salt until combined and completely smooth. Set aside.
- Place an oven rack in the middle of the oven and preheat to 350ºF (180ºC). Grease a 9 by 13 inch (23 by 33 cm) baking pan and line it with a parchment sling.
- In a small bowl, whisk together the flour, salt, and baking powder.
- In a small bowl, whisk together the eggs, granulated and brown sugars, canola oil, and vanilla.
- Put the butter and chocolate in a small, heavy-bottomed saucepan over low heat and melt them together, stirring often so the chocolate doesn't scorch. Keep cooking until the mixture is smooth. Off the heat, whisk the cocoa powder into the chocolate until fully combined.
- Add the chocolate mixture to the sugar and egg mixture and whisk until smooth. Then add the flour mixture and stir until just combined.
- Pour the brownie batter into the prepared pan. Dollop the peanut butter filling and marshmallow creme over the top, alternating between the two. Drag the tip of a butter knife through the batter to create swirls.
- Bake until the edges have set, the top looks glossy and starts to crackle, and a wooden skewer or toothpick inserted into the center comes out with crumbs, 26 to 32 minutes. The skewer should not come out wet, but it should have plenty of crumbs clinging to it.
- Move the pan to a wire rack and let it cool completely. Use the parchment sling to lift the brownies out of the pan gently, then cut them into bars and serve. Store leftovers in an airtight container at room temperature for up to 2 days.
Baker’s notes
- Marshmallow Peanut Butter Brownies recipe reprinted with permission from 100 Cookies cookbook author Sarah Kieffer and Chronicle Books LLC.
- Use the parchment sling. It makes it much easier to remove the brownies from the pan to cool, and cutting them becomes simple too!
- Warm the Marshmallow Fluff. Microwaving the marshmallow fluff for 15 seconds made it much easier to dollop onto the brownies.
- Microwave Method for Melting Chocolate and Butter. Heat for 45 – 60 seconds on medium power. Stir, then repeat until both ingredients have fully melted and are smooth. Stir in the cocoa powder afterward.
- Make the peanut butter filling first. This is a small time-saver. Once the brownie batter is in the pan, dollop on the peanut butter filling and marshmallow fluff right away.
