2 cups sugar
1/2 teaspoon salt
2 cups 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 teaspoons vanilla extract
1 bag miniature marshmallows
Icing:
1 stick unsalted butter, softened
3 tablespoons cocoa
6 tablespoons milk
1 (1-pound) box confectioners' sugar
1 cup chopped pecans or walnuts
1 teaspoon vanilla extract