Mississippi Mud Cake

This cake reminds me of the Marshmallow Brownies we use to make growing up. The cake and frosting are similar to a Texas Sheet cake. Enjoy!

2 cup sugar
1/2 teaspoon salt
2 all-purpose flour
1 stick unsalted butter
1/2 cup vegetable oil
1/2 cup cocoa
1/4 cup water
2 eggs
1 teaspoon baking soda
1/2 cup buttermilk
2 teaspoon vanilla extract
1 bag miniature marshmallows

Icing:
1 stick unsalted butter, softened
3 tablespoon cocoa
6 tablespoon milk
1 (1-pound) box confectioners' sugar
1 cup chopped pecans or walnuts
1 teaspoon vanilla extract

Preheat the oven to 350 degrees F. Grease and flour a 13 by 9-inch baking pan.
Combine the sugar, salt, and flour in a large mixing bowl. Bring the butter, oil, cocoa, and 1/4 cup water to a boil in a saucepan. Add to the flour mixture.
Beat together the eggs, baking soda, buttermilk, and vanilla. Add to the chocolate mixture, mix well, and pour into the prepared pan. Bake for 25 minutes.
While the cake is baking, make the icing by melting the butter in the cocoa and milk over low heat. Bring the mixture to a boil. Remove from heat and stir in the confectioners' sugar until smooth. Slowly stir in the nuts and the vanilla. Take the cake from the oven, and cover it with miniature marshmallows. Pour the warm icing over the cake and the marshmallows. Cool the cake before serving.