Mississippi Mud Brownies

These Mississippi mud brownies are an easy decadent treat! Made with fudgy brownies made without a mixer, then topped with mini marshmallows and an easy stovetop fudge icing poured over the top.

 

Rich, gooey, messy-in-the-best-way brownies — this Mississippi Mud Brownies recipe is exactly the kind of nostalgic bake that disappears fast. Every time I make them, someone says, “You need to make these again.” Kind of like my Mississippi mud cake or Mississippi mud pie– just in brownie form!

They start with a fudgy brownie base (not cakey!), get topped with puffy melted marshmallows, and are finished with a silky chocolate icing that drips beautifully into the marshmallow layer. They make 24 generous bars, which is why they’re perfect for holidays, potlucks, church gatherings, or anytime you want to impress a crowd… with very little effort.

No fancy tools required — just a whisk, a saucepan, and one baking pan. If you love indulgent chocolate desserts that feel extra special, these are for you.

Ingredients You’ll Need

• All-purpose flour
• Salt
• Baking powder
• Eggs
• Granulated sugar
• Brown sugar – If you run out, try my homemade brown sugar.
• Oil – You want to use a neutral-tasting oil such as vegetable oil or canola oil.
• Vanilla extract
• Butter – I used unsalted butter, but salted butter will also work. Just reduce the salt.
• Semi-sweet or bittersweet chocolate, chopped – I don’t recommend chocolate chips as they contain stabilizers and can prevent them from melting.
• Dutch process cocoa powder – You can use natural unsweetened cocoa powder but the brownies will not be as rich or intensely chocolate.
• Mini marshmallows
• Powdered sugar – If you run out, try my homemade powdered sugar.
• Milk – Any milk will work.

How to Make Mississippi Mud Brownies

Step 1: Prep Your Pan

Preheat your oven to 350°F (180°C). Line a 9×13″ baking pan with parchment paper or grease it well.
A metal pan bakes brownies most evenly, but glass works too — just expect an extra minute or two of bake time.

Step 2: Mix Dry Ingredients

In a small bowl, whisk flour, salt, and baking powder. Set aside.

Step 3: Combine the Sugars and Eggs

In a large bowl, whisk together granulated sugar, brown sugar, eggs, oil, and vanilla until smooth.

Step 4: Melt the Chocolate

In a small saucepan over low heat, melt butter and chopped chocolate together, stirring so nothing scorches.

Remove from heat and whisk in cocoa powder until silky. By whisking the cocoa powder into the hot butter mixture at this point helps to bloom the cocoa powder and bring out the chocolate taste.

Step 5: Bring It All Together

Whisk the warm chocolate mixture into your sugar mixture until smooth.
Add dry ingredients and gently stir until combined — stop as soon as you no longer see dry streaks. Overmixing = tougher brownies.

Spread batter evenly in the prepared pan and bake for 22–27 minutes, or until a toothpick inserted comes out with moist crumbs. Don’t overbake! Fudgy brownies come from not overbaking. So be careful!

Step 6: Add the Marshmallows

Once they are baked remove them from the oven. Scatter mini marshmallows evenly over the warm brownies.

Return to the oven for 3–5 minutes — just until they puff. You don’t want them browned, just pillowy.

Step 7: Make the Icing

While the brownies cool slightly, melt butter in a saucepan over medium heat.

Whisk in cocoa powder and salt until smooth, then remove from heat.

Stir in vanilla, then gradually whisk in powdered sugar and milk until you have a pourable, glossy icing.

Step 8: Finish + Cool

Drizzle the warm icing over the marshmallows. You can gently spread it with an offset spatula so it glides across the top without tearing the marshmallow layer.

Now, the hardest part — let the brownies cool completely before slicing. This helps the icing set into the marshmallows and gives you clean squares.

Storage

Store these at room temperature for up to 3 days or in the fridge for about a week.
They freeze beautifully too — wrap individually and thaw when a chocolate craving hits.

More Brownies to Bake Next

If you’re craving more brownies then be sure to try my M&M brownies. They use the same brownie base and are loaded with M&M’s! Or try these Buckeye brownies if you’re a peanut butter lover.