Fudgy brownie bottom with a drizzly marshmallow top, this dessert is tasty warmed up as well as chilled. Impressive to look at and even better to eat, these chewy Mississippi mud brownies make a great addition to any potluck or family gathering.

Mississippi mud brownies on a cooling rack.

The History Behind Mississippi Mud Brownies

The story goes that Mississippi mud brownies originated in the South during World War II when home cooks were excited to use commercial ingredients (such as mini marshmallows) in their desserts. The combination of chocolate chips, marshmallows, and chocolate drizzle was said to resemble the muddy banks of the Mississippi River. As a Southerner living in the Midwest, making these brownies takes me back to my high school days when my mother would pull out a batch from the freezer on a hot summer day so that my siblings and I could enjoy them with friends while playing by the pool. The only way to dislike these is to be allergic to chocolate!

An overhead view of Mississippi mud brownies.

Why You Will Love This Recipe

Rich and Gooey: Mississippi mud brownies are super-chocolatey with bites of chocolate chips, marshmallow, and chocolate drizzles.
Customizable: You can add mix-ins like nuts, peanut butter chips, shredded coconut, etc. for creative variations.
Full of Real Chocolate: This recipe uses baking chocolate, which is more concentrated than cocoa powder.
Freezer Friendly: Cut your brownies into squares and freeze for later.

The sky really is the limit with this recipe. You can make so many variations to suit your sweet tooth. You can use dark chocolate or milk chocolate drizzle, flavored marshmallows, and any combination of mix-ins. Think walnuts, pecans, pistachios, toffee bits, chopped up Reese’s candies, etc.

Mississippi mud brownies cut into squares.

The Ingredients

Unsweetened Chocolate Baking Squares (preferably Baker’s premium baking bar-better ingredients)

Butter (at room temperature)

Granulated Sugar

Eggs (at room temperature)

All Purpose Flour

Vanilla Extract (store bought or homemade vanilla extract)

Semisweet Chocolate Chips

Chocolate, butter, vanilla, sugar and eggs on a countertop. — Ingredients for the brownies.

Melting chocolates and marshmallows on a countertop. — Ingredients for the toppings.

The Equipment

Stand mixer ( like KithchenAid) with mixing bowl

Whisk attachment for mixer

Paddle attachment for mixer (also known as a flat beater)

Spatula

Whisk

Nonstick baking spray (like Baker’s Joy or La Tourangelle)

13 x 9 inch baking pan or glass casserole dish

How to Make Mississippi Mud Brownies

Step 1:

Preheat the oven to 350 degrees Fahrenheit. Assemble the tools (listed above) that you will need. In this explanation, a stand mixer (KitchenAid) is used but you can substitute with a second large mixing bowl.

Step 2:

In a stand mixer, cream the butter and sugar on medium-high speed until fluffy. Add eggs, one at a time until evenly blended.

Step 3:

Melt the baking chocolate in the microwave at 50% power. Stir every 30 seconds until melted. TIP: Although melted, the chocolate might hold its form, so be sure to mix often.

Step 4:

Add the melted chocolate to the sugar and butter mixture.

A mixture of melted chocolate, sugar, butter, and eggs in a stand mixer.

Step 5:

Mix in flour until blended. Add vanilla and chocolate chips.

Step 6:

Spread the batter into a greased 13 inch x 9 inch pan and bake at 350 degrees Fahrenheit for 35-40 minutes or until you can poke a toothpick through the center and it comes out clean.

Step 7:

Take the brownies out of the oven. Dust a light sprinkling of corn starch over the brownies. Then spread 1 ½ cups of miniature marshmallows over the top. Place the brownies back in the oven for 10 minutes or until marshmallows have slightly browned on the top.

Toasted marshmallows on Mississippi mud brownies.

Step 8:

Pull the brownies out of the oven and allow to cool completely before drizzling chocolate over them.

Step 9:

In a microwave, heat the melting chocolate until it is a liquid. Using a spoon drizzle the melted chocolate over the Mississippi mud brownies in several directions. Allow the chocolate to cool completely before cutting the brownies.

Three Mississippi mud brownie squares in a stack with a glass of milk in the background.

HELPFUL TIPS FOR MAKING MISSISSIPPI MUD BROWNIES

Stir the melting chocolate often. Chocolate baking squares like to hold their form in the microwave, so be sure to stir after every 30 seconds to prevent burning.

Do not overmix the batter in order to keep brownies more gooey and less cakey.

Use cornstarch to keep the marshmallows from separating from the brownies.

Allow the marshmallow brownies to cool completely before drizzling the melted chocolate on top.

Mix coconut oil into your melting chocolate if you need to make it smoother.