Marshmallow Peanut Butter Brownies baked to share
These Marshmallow Peanut Butter Brownies should be your next rich go-to treat! They combine rich and chewy, chocolatey brownies with marshmallow fluff and a peanut butter filling swirled all over the top! They are a fantastic recipe from the friend Sarah Kieffer's new cookbook, 100 Cookies, that are a strong match for any brownie lover in your life!
6 Reasons Why You Should Make This method
- Rich and chocolatey brownies that are right in between fudgy and cakey—the best of both worlds!
- You don't need your hand mixer OR stand mixer.
- Swirled peanut butter and marshmallows on top!
- Easy prep and takes about 26-32 minutes to bake.
- Chocolate, peanut butter, and marshmallow together are a lush trio of flavors!
- They're from Sarah Kieffer's new cookbook, 100 Cookies!
About the Author: Sarah Kieffer
Sarah is a legend when it comes to cookies and brownies! She is most widely known for her pan-banging cookies, which she dedicates an entire chapter to in her latest cookbook, 100 Cookies.
She also brings back her popular “A house favorite Brownies” recipe from her first book, The Vanilla Bean Baking Book. It's also the base recipe I used to make these marshmallow peanut butter brownies.
If you love brownies and cookies (and truly any dessert), I clearly recommend getting both her cookbooks, checking out her blog, The Vanilla Bean Blog: A Baker's Soliloquy, or give her a follow over on Instagram!
And just a little side note, Sarah is among the coolest and kindest people I've met in the baking blog world. I'm so proud of her and all she has accomplished!
Baking Tools Needed
Try the following baking tools when making these marshmallow peanut butter brownies.
- 9 x 13-inch baking pan. My Nordic Ware metal pan is my go-to baking pan for all my sheet cakes, rice krispie treats, and these brownies!
- Baker's Joy Baking Spray. I swear by this for greasing any of my baking pans. You can alternatively use a light coating of butter and dusting of flour or vegetable shortening and flour.
- Parchment paper. Not required, but it clearly helps with removing the brownies to cool and cut.
- Mixing bowls. You'll need at least 3 for this method. Two smalls and a medium is good.
- Saucepan. This is for melting the chocolate and butter together. I used my Dansk 1 quart hot cocoa pot.
- Whisks and spatulas. The whisks come in handy for mixing the dry and wet ingredients. When combining the two, a spatula does a good job there, and when you pour the batter into the pan.
- Wire cooling rack. For cooling the marshmallow peanut butter brownies.
- Large knife. A large sharp knife is always handy for cutting brownies!
How it comes together
Below is a general outline of making these marshmallow peanut butter brownies recipe with a peanut butter filling and marshmallow fluff. The full recipe is below; you can find these in Sarah's new 100 Cookies cookbook!
Make the peanut butter filling. You can easily do this in a small bowl stirring it together with either a whisk or spatula. A reliable choice is to do this step first before I make the brownies. You will need creamy peanut butter, confectioners' sugar, unsalted butter, and salt.
Whisk the dry ingredients together. This includes all-purpose flour, salt, and baking powder.
Whisk the wet ingredients. Do this in a separate mixing bowl for the eggs, canola oil, granulated and brown sugars, and vanilla extract.
Melt the butter and chocolate. Make sure to chop the chocolate into small pieces or break it up into smaller pieces and use a small, heavy-bottom saucepan. Add this to the wet ingredients and mix until well blended.
Add the dry ingredients to the wet. Mix until it is just combined.
Pour the brownie batter into the prepared pan. Don't forget to use your spatula to get all the batter out of the bowl.
Dollop, then swirl. Alternate between dolloping the peanut butter filling and marshmallow fluff. Then gently swirl together with the brownie batter using a butter knife.
Bake, then cool. These marshmallow peanut butter brownies will take anywhere from 26-32 minutes at 350ºF. Cool on a wire rack after. Make sure they are cooled completely before cutting.
Questions on this bake
Can Use the microwave to heat the chocolate and butter?Yes! Heat for 45 – 60 seconds at medium power. Stir, then repeat until both ingredients have fully melted and are smooth. Add in the cocoa powder after.
Will these brownies keep at room temperature?Yes! For up to 2 days, stored in a sealed food container. You can also keep them in the refrigerator for a day or two longer.
My Top Brownie-Making Tips
Use the parchment sling. This is helpful when removing the brownies from the pan to cool and makes cutting them easier!
Mix up the peanut butter filling first. This is just a little bit of a time saver tip. Once you pour the brownie batter into the pan, you'll want to dollop on the peanut butter filling and marshmallow fluff immediately after.
Warm up the marshmallow fluff. I found that heating it in the microwave for 15 seconds helped with dolloping it onto the top of the brownies.
Swirling 101. Just skim the top of the brownies as you swirl. I went a little too crazy with the swirling and pushed most of the marshmallow fluff to the inside. They still tasted especially good, and it was nice seeing the marshmallow peak through when you took a bite. They're just not as pretty as Sarah's!
Need More Brownies in Your Life?
The Best Salted Pecan Pie Brownies
Pumpkin Frosted Fudgy Brownies
Better Than Box Mix Fudgy Brownies
Double Chocolate Mint Brownies
- Yield 24 servings
- Prep 20 minutes
- Cook 32 minutes
- Total 52 minutes
- Calories 281
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
peanut butter filling
- In a medium bowl, stir together the peanut butter, powdered sugar, unsalted butter, vanilla, and salt until evenly mixed and completely smooth. Set to the side.
brownies
- Adjust an oven rack to the middle of the oven. Heat the oven to 350ºF (180ºC). Grease a 9 by 13 inch (23 by 33 cm) baking pan and line 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.
- Place the butter and chocolate in a small, heavy-bottom saucepan set over low heat and melt together, stirring frequently to prevent the chocolate from scorching. Continue cooking until the mixture is smooth. Off the heat, add the cocoa powder to the chocolate and whisk until completely combined.
- Add the chocolate mixture to the sugar-egg mixture and whisk until smooth. Add the flour mixture and stir until just combined.
assembling the marshmallow peanut butter brownies
- Pour the brownie batter into the prepared pan. Dollop the peanut butter filling and the marshmallow creme over the top, alternating the two. Drag the tip of a butter knife through the batter, creating swirls.
- Bake until the sides of the brownies have set, the top is starting to crackle and look glossy, and a wooden skewer or toothpick inserted into the center comes out with crumbs, 26 to 32 minutes. The batter on the toothpick should not be wet, but should have a good amount of crumbs clinging to it.
- Transfer the pan to a wire rack and allow it to cool completely. Use the parchment sling to gently lift the brownies from the pan. Cut them into bars and serve. Store brownies in an airtight container at room temperature for up to 2 days.
Baker notes
Marshmallow Peanut Butter Brownies recipe reprinted with permission by 100 Cookies cookbook author Sarah Kieffer and Chronicle Books LLC.
Use the parchment sling. This is helpful when removing the brownies from the pan to cool and makes it easier to cut them as well!
Warm the Marshmallow Fluff. I found that heating the marshmallow fluff in the microwave for 15 seconds helped with dolloping it onto the top of the brownies.
Chocolate and Butter Alternative Microwave Melting Method. Heat for 45 - 60 seconds at medium power. Stir, then repeat until both ingredients have fully melted and are smooth. Add in the cocoa powder after.
Mix up the peanut butter filling first. This is just a little bit of a time saver tip. Once you pour the brownie batter into the pan, you'll want to dollop on the peanut butter filling and marshmallow fluff immediately after.
