The brownie + marshmallows + toasted pecans + fudge sauce combo has never been tastier (or easier!). These Mississippi Mud Bars are insanely delicious and so simple to make!

These bars! Seriously, amazing. Prepare to wow your friends and family with this tasty little Mississippi Mud concoction.

I made them recently for a church event and was kind of surprised at how many people were excited about them.

Top down view of sheet pan Mississippi Mud Bars with a bar cut out and removed.

Maybe the fact that the event was a Cub Scout Pinewood Derby should be honestly disclosed. A group of energetic, mildly stinky boys (I can say this as two of them are mine) who would willingly eat crumbled off-brand Oreo crumbs off a gym floor may not be the most objective of dessert judges, I know.

But I still validate their honest feedback (even if I did have to hold the pan over my head and threaten to take the wheels off their Pinewood Derby cars if they came back for a 5th bar without washing their hands – or asking their mom first).

AND judging by the fact that many of the parents asked for the recipe, I can safely and comfortably recommend these bars for all of your future event/potluck/late night binging needs.

Three Mississippi Mud Bars stacked on top of each other on a white tray with a bite taken out of the top bar.

I was initially skeptical that these bars could fulfill my chocolate-loving dreams because the brownie/cakey base is so…well…thin.

And I don’t know about you, but “thin” as a descriptor doesn’t belong anywhere near a pan of decadent, chocolatey brownies, in my opinion.

However, the ultimate result of topping soft and rich brownies with marshmallows and then pecans and then a chocolate drizzle far, far exceeded my expectations.

The equal parts brownie to marshmallow ratio is what makes these Mississippi Mud bars so divine. Basically, thin brownies are welcome here.

White tray of Mississippi Mud Bars side by side.

The brownie cake layer (it really is a cross between a brownie and a cake in terms of texture and flavor) mixes up all in one bowl, which makes the assembly of these bars ultra-easy.

Then, once they are baked, marshmallows are dumped on top and softened for just a few additional minutes in the oven before getting a dose of toasted pecans.

And speaking of pecans, I know there are organizations dedicated to the hatred of nuts in desserts…and an equal number of people who fight the opposite side.

I’m somewhere in the middle. 99% of the time, I opt OUT of nuts in any of my brownies or cakes (total exception for these white chocolate pecan brownies and a few other divine special cases).

But without the pecans, these Mississippi Mud bars just aren’t complete, and I, personally, loved the toasty crunch. Coming from a semi-nut hater, that should give you a small push to add them if you are on the fence.

Spatula removing Mississippi Mud Bars from sheet pan.

Toasting the pecans is optional, but the level of flavor boost is pretty significant, so I definitely recommend doing it (or buying toasted pecans…I know Trader Joe’s carries them?).

Also, please make sure when you get to the step of The Chocolate Drizzle that you take great care to apply the chocolate sauce to the top of the bars in a very defined, precise, geometric pattern.

You might consider sketching the drizzling action on a sheet of graph paper first, as perfection is the only acceptable method here.


Just kidding.

Go crazy and drizzle your heart out until it looks messy and absolutely delicious.

Top down view of sheet pan Mississippi Mud Bars.

As you can see from the pictures, these Mississippi Mud bars are sheet pan style.

So great and practical for potlucks or events where you are serving a lot of people.

I know a good food blogger worth her salt would have experimented to cut the recipe down and make it in a 9X13-inch or smaller pan.

But that food blogger is not me today.

I love sheet pan recipes like this because I so often need a large and in charge dessert to take to church events or family get togethers or whatever else comes on the horizon (yes, even a night in with the family will sometimes justify an enormous sheet pan splurge).

However, as noted in the recipe, I think there’s a good chance the recipe could be halved and baked in a 9X13-inch pan. Someone report back if they try it? Thanks. 🙂

Sheet pan Mississippi Mud Bars with a bar cut out and removed.

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Spatula removing Mississippi Mud Bars from sheet pan.

Mississippi Mud Bars

4.76 stars (66 ratings)



  • 1 ⅓ cups (189 g) all-purpose flour
  • 1 cup (212 g) granulated sugar
  • 1 cup (212 g) brown sugar
  • ½ cup (43 g) unsweetened cocoa powder
  • ½ teaspoon baking soda
  • ½ teaspoon salt
  • 1 cup (227 g) salted butter, melted
  • 4 large eggs
  • 1 teaspoon vanilla extract
  • 10-ounce package (283 g) mini marshmallows
  • 1 cup (120 g) chopped pecans, toasted (optional but delicious)

Chocolate Topping:

  • cup (28 g) unsweetened cocoa powder
  • ¼ cup milk
  • ¼ cup (57 g) salted butter
  • Pinch of salt
  • 2 cups (228 g) powdered sugar
  • 1 teaspoon vanilla extract


  • Preheat the oven to 350 degrees F. Line a large, rimmed baking sheet (half sheet pan, about 12X18 inches) with parchment and lightly grease with cooking spray. Alternately, you can line with foil and grease the foil or leave the pan unlined and grease the pan.
  • For the bars, in a large bowl, whisk together the flour, sugar, brown sugar, cocoa (sift the cocoa into the bowl using a fine mesh strainer if it is overly clumpy), baking soda and salt. Add the melted butter, eggs, and vanilla. Mix together until combined (don’t overmix; just whisk/stir until no dry streaks remain and ingredients are evenly combined).
  • Spread the batter evenly in a thin layer in the prepared pan. Bake for 15-20 minutes until the top is springy to the touch and a toothpick inserted in the center comes out clean. Watch closely so the thin bars don’t overbake!
  • Remove from the oven, sprinkle the top evenly with marshmallows, and bake for 3-5 minutes more until the marshmallows are softened.
  • Sprinkle with pecans and let cool to room temperature before glazing.
  • For the chocolate topping, in a medium saucepan, whisk together the cocoa powder (I sift it in to avoid clumps), milk, butter, and salt. Bring the mixture to a gentle boil over medium heat, stirring or whisking constantly.
  • Remove from the heat and whisk in the powdered sugar and vanilla. Thin with additional milk, if needed, until the mixture is thick but pourable and can easily be drizzled across the bars.
  • Drizzle the glaze in a crisscross pattern across the bars. Serve the bars warm or at room temperature. They are easier to cut if they’ve been cooled completely.


Glaze: I prefer to glaze the bars with the chocolate sauce after they’ve cooled so the chocolate mixture doesn’t absorb/sink into the marshmallows, but if you don’t care about that, you can save time and glaze them while warm.
Halving the Recipe: I have not tried halving the recipe, but you could probably try for a 9X13-inch (or slightly smaller) pan. 
Cutting Bars: with marshmallows in them can be messy and tricky. I’ve had the best luck letting these bars cool completely (to room temperature) and using a sharp knife to cut the bars using short motions instead of dragging the knife through the bars. I also keep my kitchen shears/scissors on hand to trim any rogue pieces of marshmallow that want to stay attached when I scoop out the bars.
Serving: 1 Bar, Calories: 294kcal, Carbohydrates: 42g, Protein: 3g, Fat: 14g, Saturated Fat: 7g, Cholesterol: 53mg, Sodium: 177mg, Fiber: 2g, Sugar: 32g

Recipe Source: adapted from a recipe *I think* I tore out from the Bake From Scratch magazine