Southern Living offers a recipe for Mississippi mud cake on MyRecipes.com. The recipe calls for butter, sugar, unsweetened cocoa, eggs, flour and vanilla extract. The cake is topped with miniature marshmallow, seasoned with a touch of salt and includes chopped toasted pecans in the batter mix.
Melt 1 cup of butter, and whisk it together with 2 cups of sugar, 1/2 cup of unsweetened cocoa powder, 4 large lightly beaten eggs, 1 teaspoon of vanilla extract and 1/8 teaspoon of salt in a large bowl. Stir in 1 1/2 cups of all-purpose flour along with 1 1/2 cups of coarsely chopped toasted pecans. Grease and flour a 15-by-10-inch jelly roll pan. Pour the batter into the pan.
Bake the cake at 350 degrees Fahrenheit for 20 to 25 minutes. The cake is done baking when a wooden toothpick inserted into the center comes out clean. Remove the cake from the oven, and top with 10.5 ounces of miniature marshmallows. Place the cake back in the oven to bake for five more minutes. Remove the cake and drizzle chocolate frosting over the surface.
Allow the cake to cool completely before serving. For an easier recipe, use 2 19.5-ounce packages of brownie mix instead of making the batter from scratch. Make the brownie mix according to the package instructions, mix in the chopped pecans and bake for 30 minutes at 350 degrees Fahrenheit. Top with marshmallows and frosting.