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These Mississippi Mud Brownies stack fudgy brownies, gooey toasted marshmallows, crunchy pecans, and a glossy homemade chocolate sauce into the most decadent dessert bars, and they vanish off the dessert table at every potluck I bring them to. A boxed brownie mix shortcut makes them so easy. If you love a rich chocolate treat, our thick and chewy Butterfinger brownies are another must-bake.
Fudgy brownies, melty marshmallows, pecans, and chocolate sauce make these the ultimate easy crowd-pleasing dessert bars.
Mississippi Mud Brownies Quick Look
- 🕒 Prep Time: 20 minutes
- 🌡️ Cook Time: 25 minutes
- ⏳ Total Time: 45 minutes
- 🍽️ Serving: 12 bars
- ⚡ Calories: 259kcal
- 🌶️ Flavor Profile: Fudgy, gooey, chocolatey with toasted marshmallow and pecans
- ✋ Difficulty: Easy, on par with our Butterfinger brownies
Quick Answer
To make Mississippi mud brownies, prepare a boxed fudge brownie mix and fold in chopped pecans, then spread the batter thin on a lined sheet pan and bake about 15 minutes. Top the warm brownies with mini marshmallows and return them to the oven for a few minutes until puffed. Make a quick chocolate sauce by melting cocoa, milk, butter, and salt, then whisking in powdered sugar and vanilla. Drizzle the sauce over the marshmallows, add more pecans, cool, and slice.
Jump to:
- Mississippi Mud Brownies Quick Look
- Quick Answer
- Why This Recipe Works
- Why You’ll Love This Recipe
- Key Ingredients
- Variations and Substitutions
- How to Make Mississippi Mud Brownies
- Recipe Tips & Tricks
- Serving Ideas and Suggestions
- Mississippi Mud Brownies FAQs
- Other Recommended Chocolate Desserts
- Mississippi Mud Brownie Bars
Why This Recipe Works
Click to see the technique science
- A boxed mix keeps it easy. Starting with a fudge brownie mix means these decadent bars come together fast with foolproof results.
- Three irresistible layers. Fudgy brownie, gooey toasted marshmallow, and glossy chocolate sauce stack into pure indulgence.
- Pecans add the perfect crunch. Chopped pecans folded into the batter and sprinkled on top balance the gooey layers with toasty crunch.
- Thin bars bake fast. Spreading the batter thin on a sheet pan means a shorter bake and the ideal brownie-to-topping ratio.
- The homemade sauce is glossy and rich. A quick cocoa and powdered sugar sauce drizzles on beautifully and sets into a fudgy finish.
- They feed a crowd. One pan makes a dozen rich bars, perfect for potlucks, bake sales, and parties.
Why You’ll Love This Recipe
- They stack fudgy brownies, gooey marshmallows, pecans, and chocolate sauce into one decadent bar.
- A boxed brownie mix shortcut makes them quick and foolproof.
- They are a guaranteed potluck hit right alongside our chocolate cream cheese frosting treats.
Key Ingredients
Here is everything you need to make these decadent Mississippi mud brownies. A boxed mix and a few pantry staples do the work.
- Fudge Brownie Mix: The easy base for the bars. Grab your favorite boxed fudge brownie mix plus the eggs, oil, and water it calls for.
- Pecans: Chopped and folded into the batter and sprinkled on top for toasty crunch.
- Mini Marshmallows: Spread over the warm brownies and baked until puffed and gooey.
- Cocoa Powder: Unsweetened cocoa is the base of the rich homemade chocolate sauce.
- Butter and Milk: Melted with the cocoa to start the glossy chocolate sauce.
- Powdered Sugar: Whisked into the sauce for a smooth, sweet, drizzle-able finish.
- Vanilla and Salt: Round out and balance the chocolate sauce.
See recipe card for exact quantities.
Variations and Substitutions
These Mississippi mud brownies are easy to make your own. Here are a few favorite ways to switch them up.
- Use a different nut: Swap the pecans for walnuts, or leave them out for a nut-free version.
- Make them from scratch: Use your favorite homemade fudgy brownie recipe in place of the boxed mix.
- Add chocolate chips: Fold chocolate chips into the batter for even more chocolate.
- Top with frosting: Swap the chocolate sauce for our chocolate cream cheese frosting.
- Make them peanut buttery: Drizzle with melted peanut butter along with the chocolate sauce.
- Add a graham crust: Press a graham cracker layer on the bottom for extra texture.
How to Make Mississippi Mud Brownies
- Heat the oven to 350 degrees Fahrenheit and line a rimmed baking sheet. Prepare the fudge brownie mix according to the box directions.
- Fold the chopped pecans into the batter, then spread it into an even layer on the prepared pan.
- Bake for about 15 minutes, until a toothpick comes out clean. Because the bars are thin, the bake time is shorter than the box says.
- Top the warm brownies evenly with mini marshmallows and return to the oven for 3 to 5 minutes until puffed and soft, then cool on a wire rack.
- Make the chocolate sauce by melting the cocoa, milk, butter, and salt in a saucepan, stirring until smooth, then whisk in the powdered sugar and vanilla.
- Drizzle the chocolate sauce diagonally over the marshmallow-topped brownies, sprinkle with more pecans, cool completely, then slice and serve.
Recipe Tips & Tricks
- Spread the batter thin and even so the bars bake quickly and stay the right thickness.
- Watch the bake time; thin brownies bake faster than the box directions say.
- Add marshmallows while warm so they soften and stick to the brownie layer.
- Stir the chocolate sauce constantly over the heat so it stays smooth and lump-free.
- Thin the sauce with a splash of milk if it is too thick to drizzle.
- Drizzle, do not drown; a diagonal drizzle looks pretty and keeps them from being too sweet.
- Cool completely before slicing so the layers set and you get clean bars.
Serving Ideas and Suggestions
These Mississippi mud brownies are rich, so cut them into small squares and pile them on a platter for a dessert table. They are perfect for potlucks, bake sales, holidays, and parties, and they always disappear fast.
Serve them with a cold glass of milk or a scoop of vanilla ice cream for the ultimate treat. They are right at home on a dessert spread next to our Butterfinger brownies and chocolate covered peanut butter pretzels.
For a bigger sweets table, add a tray of oatmeal cream pie ice cream bars so there is a little something for every chocolate and marshmallow lover.
These bars keep well in an airtight container at room temperature for up to four days, making them a great make-ahead dessert for a crowd.
Mississippi Mud Brownies FAQs
Mississippi mud brownies are a decadent Southern dessert bar made of a fudgy brownie base topped with gooey toasted marshmallows, chopped pecans, and a rich chocolate sauce or frosting. They are named for their dark, gooey, mud-like layers of chocolate. This easy version uses a boxed brownie mix and a quick homemade cocoa chocolate sauce for foolproof results.
Yes, you can absolutely make them from scratch. Simply replace the boxed fudge brownie mix with your favorite homemade fudgy brownie recipe and bake it thin on a sheet pan. The rest of the recipe, including the marshmallow layer and homemade chocolate sauce, stays exactly the same. The boxed mix is just a convenient shortcut.
The key is to add the mini marshmallows after the brownies have baked, then return the pan to the oven for only 3 to 5 minutes, just until the marshmallows puff and soften. Keep a close eye on them, since they can go from golden to burnt quickly. You want them gooey and barely toasted, not browned.
Yes, these bars are great for making ahead. Bake and assemble them completely, let them cool, then store in an airtight container at room temperature for up to four days. You can also make them a day ahead for a party. The chocolate sauce sets up as they sit, making them easier to cut and serve.
Let the bars cool completely so the chocolate sauce and marshmallow layers set before slicing. For the cleanest cuts, use a sharp knife and wipe it clean between cuts, or chill the pan for 20 minutes first. Lining the pan with parchment also lets you lift the whole slab out to cut it on a board.
Store Mississippi mud brownies in an airtight container at room temperature for up to four days, or in the refrigerator for up to a week. If stacking them, place parchment paper between the layers so the sticky chocolate and marshmallow do not stick together. They can also be frozen for up to two months; thaw at room temperature before serving.
Love a rich chocolate treat? Try our thick and chewy Butterfinger brownies next.
Mississippi Mud Brownie Bars
Ingredients
- 1 box fudge brownie mix plus ingredients needed on the back of the box
- 1 cup chopped pecans plus more for garnish
- 10 ounce bag mini marshmallows
For Chocolate Sauce:
- ⅓ cup unsweetened cocoa powder
- ¼ cup milk
- ¼ cup unsalted butter
- ¼ teaspoon salt
- 2 cups powdered sugar
- 1 teaspoon vanilla extract
Instructions
- Heat oven to 350°F. Line a 9×11 rimmed baking sheet with parchment paper or baking cooking spray.
- In a large bowl, make the brownie mix box based on the directions on the box.1 box fudge brownie mix
- Fold in the chopped pecans. Spread the batter into an even layer on the prepared pan.1 cup chopped pecans
- Bake in the oven for 15 minutes or until a toothpick inserted comes out clean. Because the bars are going to be thin, the bake time will be much shorter than the directions say on the box.
- Remove the brownies from the oven and coat with the mini marshmallows evenly.10 ounce bag mini marshmallows
- Place back into the oven for 3-5 minutes until the marshmallows have puffed and become soft.
- Remove from the oven and let cool on a wire rack.
- In a medium saucepan, make the chocolate sauce by combining the cocoa powder, milk, butter, and salt over medium heat, stirring constantly. Once it is all melted, and combined with zero lumps, remove from the heat.⅓ cup unsweetened cocoa powder, ¼ cup milk, ¼ cup unsalted butter, ¼ teaspoon salt
- Add the powdered sugar and vanilla, whisking together until smooth and creamy. If the sauce is a bit thick for drizzling over the bars, then add a little more milk to thin out2 cups powdered sugar, 1 teaspoon vanilla extract
- Pour the chocolate sauce diagonally all over the mud brownie bars and add more pecans if desired. Allow to cool completely, then slice and serve.
Notes
- Parchment paper makes removal from the pan a breeze and helps with cleanup.
- For fudgy brownies, avoid overbaking by checking doneness a few minutes early.
- Let the brownie bars cool completely on a wire rack before adding the chocolate sauce.
- Room temperature ingredients ensure the batter mixes evenly and bakes perfectly.
- Make sure they are completely cool before cutting.
Nutrition
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Thanks so much, glad you loved them!
Sweet, sticky, easy to make. Pretty on the table. I really like this recipe for a quick made dessert.