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Mississippi Mud Brownies

Mississippi Mud Brownies have a sweet brownie base, topped with peanut butter, marshmallows, pecans, and a light chocolate frosting.  They are irresistible! 

Mississippi Mud Brownies

Note: This post has been updated on 5/31/17 with new photos, however the post content and recipe remain the same!  

As my most frequent dining buddy, Marc got nominated as my official taste tester.  It doesn’t sound like a rough job, but for a guy who thinks food is “good” or “okay,” sometimes it’s hard getting a lot of feedback from him.  These Mississippi Mud Brownies, though?  I definitely got a response!

Mississippi Mud Brownies
When he tried these Mississippi Mud Brownies and said “These are the best brownies I have ever had” I thought he was just being a smart ass.  It turns out, he was being serious and they really are the best brownies he’s ever had.  After eating two three way too many of these brownies myself, I’m gonna have to agree with the guy.  There are just so many layers of deliciousness going on!

Mississippi Mud Brownies

Layers of Mississippi Mud Brownies

The bottom layer is a dense and fudge-like brownie which is super easy to whip up.

The brownie layer is topped with crunchy peanut butter, marshmallows, and pecans.  Oh. Em. Gee.

Then to top it all off there is a thin chocolate frosting that seeps into all of the little crevices between the marshmallows and pecans.  If that isn’t the best brownie ever, I don’t know what is.

Mississippi Mud Brownies

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Mississippi Mud Brownies

Mississippi Mud Brownies

Mississippi Mud Brownies have a sweet brownie base, topped with peanut butter, marshmallows, pecans, and a light chocolate frosting.  They are irresistible! 
Print Pin Rate
Course: Dessert
Cuisine: American
Keyword: brownie, chocolate, marshmallows, peanut butter, fudge, pecans
Prep Time: 25 minutes
Cook Time: 28 minutes
Total Time: 53 minutes
Servings: 16 brownies
Calories: 359kcal
Author: Taylor


For the brownie layer:

  • 1/2 cup 1 stick unsalted butter, at room temperature
  • 1 cup white sugar
  • 3/4 tsp pure vanilla extract
  • 2 eggs
  • 3/4 cup all-purpose flour
  • 2 tbsp unsweetened cocoa powder
  • 1/2 tsp salt
  • 3/4 cup semi-sweet chocolate chips

For the peanut butter layer:

  • 1/2 cup crunchy peanut butter
  • 1 1/2 tsp canola oil

For the marshmallow layer:

  • 2 cups mini marshmallows

For the topping:

  • 1/2 cup chopped and toasted pecans

For the frosting:

  • 1/4 cup 4 tbsp unsalted butter
  • 2 tbsp unsweetened cocoa powder
  • 1/4 cup plus 2 tbsp milk
  • 2 cups confectioners' sugar
  • 1/8 tsp salt
  • 1/4 tsp vanilla extract


  • Preheat oven to 350 degrees F. Line 8x8" square baking pan with parchment paper or foil. If using foil, spray it with cooking spray.
  • In medium bowl, combine flour, cocoa powder, and salt. Set aside.
  • In large mixing bowl, beat together butter, sugar, and vanilla until creamy.
  • Add the eggs one at a time.
  • Stir dry ingredients into batter.
  • Pour batter into prepared pan and spread evenly.
  • Sprinkle with chocolate chips. Bake in preheated oven for 22-25 minutes.
  • When brownie layer is done baking, combine peanut butter and oil in a microwave safe bowl or measuring cup and microwave on high for 20 seconds to soften.
  • Pour this warm mixture over hot brownie.
  • Sprinkle the peanut butter covered brownies with marshmallows.
  • Return to oven to bake for 3 more minutes, or until the marshmallows puff.
  • Sprinkle puffed marshmallows with toasted pecans.

Make the frosting:

  • To make frosting, in small saucepan, melt butter over medium heat. When butter is melted, add the cocoa powder and 1/4 cup of the milk and heat until the mixture begins to boil.
  • Remove from the heat and combine with confectioners sugar and salt in a separate bowl and beat on high speed with an electric mixer until smooth and glossy.
  • If frosting is not pourable at this point, add remaining 2 tbsp of milk (I didn't have to do this).
  • Lastly, beat in vanilla, then pour evenly over puffed marshmallows.
  • Let cool completely in refrigerator for 1-2 hours.
  • Cut into squares and enjoy!


Calories: 359kcal | Carbohydrates: 44g | Protein: 5g | Fat: 19g | Saturated Fat: 9g | Cholesterol: 44mg | Sodium: 145mg | Potassium: 151mg | Fiber: 2g | Sugar: 35g | Vitamin A: 306IU | Calcium: 23mg | Iron: 1mg
Tried this recipe?Mention @greensnchocolate to let me know!
Need more ideas?Find all of my recipe pins @greenschocolate

Mississippi Mud Brownies

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Recipe Rating

  1. Oh my gosh, this is the kind of bar that one only dreams of but never imagines that such a thing could exist. I love how chock full of goodies it is. I have a huge sweet treat linky party going on at my blog and I’d like to invite you to come by and link this up.

  2. These definitely look like big yummy brownie! I love marshmallows mixed in with nuts because of the texture contrast.

    Ps. I totally have a friend who can’t use adjectives to describe my food! It annoys me so much too! I want to know details, not just “it’s so yummy!”

  3. wow!!! those look heavenly.. as do the double choc double peanut butter cookies on the bottom linky thing!


  4. Yowza! That looks like something my husband would demolish in minutes – he loves marshmallows! Great job!

  5. That looks like the best meal ever!! Yum! Thanks for sharing! I’ve linked to you on my blog – taking the Mississippi brownie to South Africa!