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Mississippi Mud Brownies

This Mississippi Mud Brownies recipe is the BEST recipe! It’s a family favorite recipe full of chocolate flavor. It doesn’t get any better!

What I love about this recipe

Full of gooey marshmallows, these brownies are one of my best chocolate desserts. The homemade chocolate sauce puts them over-the-top delicious but is so easy to make. 

Frequently Asked Questions about this Mississippi Mud Brownie recipe

Can these brownies be made in a 9- x 13-inch pan?

Yes. They will obviously be thinner, but wider. I recommend checking them at 15 minutes for doneness.

Can I use marshmallow fluff instead of the miniature marshmallows?

Probably, although you should expect the topping to be softer than the miniature marshmallows.

If I don’t want to use a boxed brownie mix, can you recommend a recipe for traditional brownies?

This is an excellent recipe for homemade chocolatey brownies. Just know, though, that it makes 2 square pans. So you’ll either need to double the ingredients for the top of the brownies (the marshmallows and chocolate topping) OR cut the brownie recipe in half.

Can I substitute vegetable oil for the butter?

Yes. Many people prefer brownies made with oil. I tend to bake more often with butter, but any neutral-flavored cooking oil will work.

Hand picking up a Mississippi Mud Brownie
  • eggs
  • butter
  • double chocolate premium brownie mix box
  • miniature marshmallows
  • unsweetened chocolate
  • heavy whipping cream
  • powdered sugar
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Mississippi Mud Brownies

Mississippi Mud Brownies

  • Author: Regan at This Baking Life
  • Total Time: 45 minutes
  • Yield: 16 servings


This Mississippi Mud Brownie recipe is AMAZING! Your whole family will love these.


  • 2 large eggs
  • 1/2 cup (4 oz.) melted butter
  • 2 tablespoons tap water
  • 1 (18-oz.) double chocolate premium brownie mix box (I used ALDI Specially Selected)
  • 1/2 (10-oz.) pkg. miniature marshmallows (about 2 1/4 cups)
  • 1 (4-oz.) semi-sweet chocolate baking bar, broken into squares or 4 oz. semi-sweet chocolate chips
  • 1/2 cup half and half
  • 1/2 cup powdered sugar, plus more to taste


  1. Preheat oven to 350 degrees F. Line a square baking pan or dish with parchment paper leaving a 1-inch overhang on 2 sides of pan.
  2. Stir together brownie mix, eggs, butter, and water in a medium bowl until smooth. Pour brownie batter into prepared pan, spreading to edges.
  3. Bake, uncovered, until a wooden pick inserted in center comes out with a few moist crumbs, 33 to 35 minutes. (Cook times may vary depending on brand of brownie mix.)
  4. During last 5 minutes of cook time for brownies, place chocolate and 1/2 cup half-and-half in a microwave-safe bowl; microwave on HIGH in 15-second intervals, stirring after each interval (be careful not to overcook or chocolate will seize) until chocolate is melted, 45 to 60 seconds total. (Mixture will not be smooth at this point.)
  5. Whisk in 1/2 cup powdered sugar, whisking until smooth and glossy. Add additional powdered sugar, 1 tablespoon at a time, as needed to sweeten chocolate mixture. 
  6. Remove from brownies from oven. Pour about half of chocolate mixture over hot brownies and carefully smooth out evenly over top of brownies. Top evenly with mini marshmallows, and spoon remaining chocolate mixture over marshmallows.
  7. Place brownies on a wire rack, and let stand at room temperature until completely cool, about 2 hours. (Place brownies in refrigerator for 1 hour for easier cutting.)
  8. Using parchment paper overhang, lift cooled brownies from pan, and cut into squares using a sharp knife. Store in an airtight container or wrap tightly in plastic wrap.


If preferred, you can substitute 1 cup of storebought chocolate frosting or chocolate icing (heated in microwave) for the homemade chocolate sauce.

I prefer to make any type of bar cookie or squares using this parchment paper-lined dish method. It makes them easier to lift from the pan and cut cleanly. If preferred, you can use aluminum foil in place of the parchment paper. Or you can skip the lining step altogether and coat the pan or dish with baking spray or cooking spray.

  • Prep Time: 10 min
  • Cook Time: 35
  • Category: Dessert
  • Method: Baking
  • Cuisine: American


  • Serving Size: 1 brownie
  • Calories: 300
  • Sugar: 27 g
  • Sodium: 180 mg
  • Fat: 17 g
  • Carbohydrates: 40 g
  • Fiber: 2 g
  • Protein: 3 g

Keywords: mississippi mud brownies

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