Irresistible Mississippi Mud Brownies include an easy homemade brownie recipe topped with warm gooey marshmallows and chocolate frosting. 

A Mississippi Mud Brownie on a baking sheet with other cut brownies.

There are so many things to love about this Mississippi Mud Brownie recipe, which is why it’s a guaranteed crowd pleaser!  This recipe was inspired by my Mississippi Mud Cake recipe that has gone viral on facebook–it’s has nearly 30 MILLION views. Obviously you all love the chocolate/marshmallow combo as much as I do, so this brownie version is only appropriate.

How to make Mississippi Mud Brownies:

  • Make the brownie batter. Mix cocoa powder and oil. Add softened butter and mix until smooth. Add sugar and mix well. Add eggs, one at a time, mixing after each addition. Add vanilla. Stir in flour and salt, just until combined.
Three process photos for making brownie batter.
  • Bake. Pour batter into greased 9×13 inch pan and bake at 350 degrees F for 25-30 minutes or until a toothpick inserted into the center comes out clean.
  • Add Marshmallows. Remove brownies from the oven and sprinkle the marshmallows evenly on top. Return to the oven for 2-3 minutes or until the marshmallows are puffed. Remove from oven and allow them to cool completely. Once brownies are cool, make the frosting.
A pan of baked brownies, then marshmallows added on top.
  • Make the Frosting. Add melted butter, cocoa powdered, evaporated milk, vanilla, and 2 cups of powdered sugar to a mixing bowl and beat with electric beaters until smooth.  Add more powdered sugar, a cup at a time, mixing well, until you reach your desired frosting consistency. I usually use about 3 ¼ cups powdered sugar. Spread frosting over the cooled brownies.
A pan of brownies with homemade chocolate frosting on top.

Pro Tip for Cutting Frosted Brownies: Use a plastic knife! The frosting and marshmallows will cut smoother and easier, without making a sticky mess, if you use a plastic knife to cut the brownies. 

Make Ahead and Freezing Instructions:

To Make Ahead: I almost like these brownies even better the second day. Something about the way the flavors blend together and settle after several hours makes them even more irresistible. I also feel like they’re a little less “rich” on day two, and they are easier to cut. But, it may be hard to wait that long, so feel free to dig in right away. The frosting can be made up to 2 weeks in advance, stored in an airtight container in the fridge. 

To Freeze: The brownies can be frozen frosted or unfrosted, covered well, for up to 3 months. Allow to come to room temperature before serving. 

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Recipe

Mississippi Mud Brownies cut into squares.
Prep 20 mins
Cook 25 mins
Total 45 mins
Add to Meal Plan

Video

Ingredients
  

For the Brownies:

  • 1/3 cup unsweetened cocoa powder
  • 1/2 cup oil (vegetable or canola oil)
  • 1/2 cup butter , softened
  • 2 cups granulated sugar
  • 4 large eggs
  • 2 teaspoons vanilla extract
  • 1 1/2 cups all-purpose flour
  • 1 teaspoon salt
  • 3 cups mini marshmallows

For the Frosting:

  • 1/2 cup butter , melted
  • 1/3 cup unsweetened cocoa powder
  • 1/3 cup evaporated milk
  • 1 teaspoon vanilla extract
  • 3 – 3 1/2 cups powdered sugar

Instructions
 

  • Preheat oven to 350 degrees F. Grease a 9×13” pan with non-stick cooking spray.
  • In a large mixing bowl, pour oil over cocoa powder and mix.
    Oil and cocoa powder in a mixing bowl to make brownies.
  • Add softened butter and mix until smooth. Add sugar and mix for 1 minute. Add eggs, one at a time, mixing after each addition. Add vanilla and mix.
    Sugar, butter, oil creamed together.
  • Add flour and salt and stir to combine. 
    Flour and salt added to wet ingredients to make brownie batter.
  • Pour batter into prepared pan. Bake for 25-30 minutes or until a toothpick inserted into the center comes out clean.
    A pan of baked brownies.
  • Remove brownies from the oven and sprinkle the marshmallows evenly on top. Return to the oven for 2-3 minutes or until the marshmallows are puffed. Remove from oven and allow them to cool completely.
    A pan of baked brownies with marshmallows on top.
  • Once brownies are cool, make the frosting.

For the frosting:

  • Add melted butter, cocoa powdered, evaporated milk, vanilla, and 2 cups of powdered sugar to a mixing bowl and beat with electric beaters until smooth. 
    The ingredients for chocolate frosting, in a mixing bowl.
  • Add more powdered sugar, a cup at a time, mixing well, until you reach your desired frosting consistency. I usually use about 3 ¼ cups powdered sugar.
    A mixing bowl with homemade chocolate frosting.
  • Spread frosting over the cooled brownies and cut into squares. I’ve found a plastic knife works best to cut them, or if you make them 1 day in advance they are much easier to cut.

Notes

Tip for Cutting Frosted Brownies: Use a plastic knife! The frosting and marshmallows will cut smoother and easier, without making a sticky mess, if you use a plastic knife to cut the brownies. 
Rocky Road Brownies: Mix in 1 cup nuts to the brownie batter, or add nuts at the same time as the marshmallows.
Make Ahead Instructions: I almost like these brownies even better the second day. Something about the way the flavors blend together and settle after several hours makes them even more irresistible. I also feel like they’re a little less “rich” on day two, and they are easier to cut. But, it may be hard to wait that long, so feel free to dig in right away. The frosting can be made up to 2 weeks in advance, stored in an airtight container in the fridge. 
Freezing Instructions: The brownies can be frozen frosted or unfrosted, covered well, for up to 3 months. Allow to come to room temperature before serving. 

Nutrition

Calories: 245kcalCarbohydrates: 29gProtein: 2gFat: 13gSaturated Fat: 5gCholesterol: 52mgSodium: 185mgPotassium: 67mgFiber: 1gSugar: 20gVitamin A: 290IUVitamin C: 0.1mgCalcium: 20mgIron: 0.9mg

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I originally shared this recipe May 2017. Updated January 2021.

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About The Author

Lauren Allen

Welcome! I’m Lauren, a mom of four and lover of good food. Here you’ll find easy recipes and weeknight meal ideas made with real ingredients, with step-by-step photos and videos.

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Comments

  1. How far in advance can I make these? I am needing to serve 100 on Tuesday morning but won’t have time to make them over the weekend. Could I make them on Friday and serve them on Tuesday?

  2. I’ve been searching for this recipe for my southern husband. His mother died a few years back and she used to make a Mississippi mud pie. It sounds just like this , it was a brownie base with marshmallow fluff, except he said it had pecans. Would you just stir the pecans into the frosting?

  3. 5 stars
    I made these for the grandkids and they loved them! They are very rich but absolutely delicious! And, they are very easy to make. Thank you for this recipe.

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