Brownies with Marshmallows and Rice Krispies

There are brownies and then there are Peanut Butter Chocolate Chip Marshmallow Rice Krispie Brownies. You read that right! And if you think that’s a mouthful, wait until you get a mouthful of this decadent dessert. This over the top rice krispie treats brownie is the perfect dessert recipe any time of the year. And if you want to bring something to a party or a bake sale that people will absolutely swoon over? This is it. You’ll always leave with an empty pan and a lot of new friends.

Original post: January 2011 | Updated: February 2021 and October 2024

Why This Recipe Works

• There’s not a more decadent brownie recipe on planet earth. Or possibly any planet.
• It’s simple math: Reese’s + marshmallows + Rice Krispies cereal + fudgy brownies = HEAVEN.
• If you want to bring something to a party that people will swoon over? This is it. You’ll always leave with an empty pan and twelve recipe requests.
• It’s the perfect dessert to make any time of the year.
• These triple layer brownies freeze so well.

Sing it with me now, because once you get a taste of these ridiculously delicious Marshmallow Chocolate Peanut Butter Rice Krispie Brownies, your mouth will be so full you won’t be doing any talking! It goes to the tune of Supercalifragilisticexpialidocious:

“Peanut Butter, Chocolate Chips, Marshmallows, Rice Krispies, once you taste these brownies you will know what life’s been missing.”

Honestly, I don’t think there’s a more decadent brownie on the planet. With brownies, peanuts, marshmallows, Reese’s peanut butter cups, chocolate, peanut butter and Rice Krispies all in a single bite, what’s not to love? This brownie has something for everyone!

It’s the perfect dessert any time of year and these rich chocolate chewy brownies make the most amazing potluck option. Just be sure to have at least a dozen copies of the recipe printed and ready to hand out for those who ask for it. Seriously.

Ingredients for Gooey Marshmallow Brownies

This easy recipe starts with boxed brownies and uses simple ingredients to create the most decadent dessert.

Family size box of brownie mix – Don’t forget to peek at the box to make sure you have all ingredients needed from the box mix instructions to make them.

Salted peanuts 

Reese’s peanut butter cups – Use fun size or regular. You’ll want 1 cup total when chopped. Or replace the chopped Reese’s peanut butter cups with equal amounts of Reese’s candies for added color and texture.

Miniature marshmallows – The softer the better.

Semisweet chocolate chips – Milk or dark chocolate can also be used.

Creamy peanut butter – For extra crunch, use crunchy peanut butter.

Rice Krispie cereal – Or other crispy rice cereal brand.

How To Make Brownies with Marshmallows and Rice Krispies

Step 1

Coat a 9×13 baking dish with cooking spray. Mix the brownie batter and bake brownies in the prepared pan according to package directions.

Step 2

Remove the baked brownies from the oven and top the brownie base with the peanuts, peanut butter cups, and marshmallows.

Return the pan to the oven and bake at 350 degrees for an additional 5 minutes, or until the marshmallows puff and brown and the chocolate begins to melt.

Step 3

In a medium bowl, combine chocolate chips with the peanut butter. Microwave on high in a microwave-safe bowl for 1 minute and stir until creamy. Add the Rice Krispies to the chocolate peanut butter mixture and stir until completely coated.

Step 4

Pour the chocolate-peanut butter topping in an even layer over top of the brownies. Refrigerate for a minimum of 2 hours before cutting into squares and serving.

Recipe Notes for the Best Brownies

• Replace the peanuts with pecans or walnuts for a different nutty flavor.
• Add peanut butter chips, butterscotch chips, or white chocolate chips for a different vibe.
• Use flavored marshmallows for seasonal brownies.
• Try the recipe using marshmallow fluff for the marshmallow layer.
• For an even bigger chocolate flavor, use cocoa krispies cereal.

How To Cut Brownies Cleanly

• Let the brownies cool completely before slicing. You might even want to refrigerate them briefly to chill.
• Use a sharp knife with a straight, non-serrated blade.
• Slice through cleanly instead of sawing the knife back and forth.
• Clean the blade of the knife between each slice with a damp, warm towel.
• Use a thin blade rubber spatula or run the back of the knife tip along the edges to make sure they aren’t sticking to the edge of the pan.

What To Do With Leftover Marshmallows

• Add to Hot Cocoa or make these delicious Hot Chocolate Cookies
• Make Easy Marshmallow Popcorn Balls
• Mix up a batch of S’Mores Snack Mix
• Eat them by the handful out of the bag!

How to Serve These Homemade Brownies

Serve these fudgy chocolate brownies on their own or topped with a scoop or two of ice cream, chocolate sauce, and lots of whipped cream for the most amazing brownie sundae.

How To Store Brownies To Keep Them Fresh

Allow the brownies to cool completely before wrapping or storing. This will help prevent condensation from forming during storage.

Place the brownies in an airtight container or wrap them well with plastic wrap. Stored at room temperature, leftover brownies will be good for up to 3-4 days. 

You can extend their shelf life to up to 2 weeks by storing them in the refrigerator. Allow refrigerated brownies to sit at room temperature for about an hour before serving. You can also warm them slightly in the microwave if you don’t want to wait.

How To Freeze Brownies

Wrap cooled brownies in a layer of plastic wrap then in a layer of aluminum foil. I also like to put a small square of parchment paper between the fudge brownies so they don’t freeze together.

Place the wrapped brownies in a freezer safe bag or container. Date and freeze for up to 4 months. Allow to thaw completely in the fridge or at room temp before serving.

How to Warm Brownies

You can warm refrigerated brownies slightly by placing them in the microwave and heating on high for 15-20 seconds.

More Brownie Recipes

• Reese’s Cheesecake Brownies are the best of all dessert worlds! Cheesecake, brownies, chocolate and peanut butter all in a single bite! This is the BEST kind of party food. It’s the first thing to get devoured every single time!
• Meet Chocolate Caramel Brownies, my favorite brownie recipe of all time. These are the BEST brownies you will ever eat! Hide the caramel in the middle for a delicious surprise. Bring these to parties and people will love you.
• Gluten Free Chocolate Brownies – This brownie is my FAVORITE gluten-free dessert recipe. You’ll never know that they are gluten free. These babies are chocolatey, delicious and irresistible!
• Mint Chocolate Brownies – Delicious mint frosting sandwiched between perfect, chocolatey brownies and creamy chocolate. Take your next pan of brownies to the next level by combining fudgy and minty!