3 cups all-purpose flour
3 cups white sugar
3/4 teaspoon salt
1 1/2 cups margarine
1 1/2 cups water
4 1/2 tablespoons unsweetened cocoa powder
1 cup buttermilk
1 1/2 teaspoons baking soda
1 teaspoon vanilla extract
1/2 cup margarine
6 teaspoons milk
3 tablespoons unsweetened cocoa powder
4 cups confectioners' sugar
Preheat oven to 350 degrees. Grease a 12 X 18-inch jelly roll pan.
Sift flour, white sugar, and salt together in a large bowl.
Combine 1 1/2 cups margarine, water and 4 1/2 tablespoons cocoa together in a saucepan; bring to a boil. Pour margarine mixture over flour mixture; stir to combine.
Beat buttermilk, eggs, baking soda, and vanilla extract together in a bowl; add to margarine mixture and stir until batter is combined. Pour batter into prepared pan.
Bake in the preheated oven until a toothpick inserted into the center of the brownies comes out clean, about 20 minutes. Cool completely.
Heat 1/2 cup margarine, milk and 3 tablespoons cocoa powder together in a small saucepan over low heat until margarine melts and mixture is combined; remove from heat. Beat confectioners' sugar into margarine mixture until frosting is smooth and creamy. Spread frosting over cooled brownies and cut into squares.
Bake 20 minutes.