Sift together into mixing bowl:

2 c. flour
1 3/4 c. sugar
1/4 tsp. salt
4 tbsp. cocoa

Bring to boil:

1 c. cold water
1/2 c. salad oil
1/2 c. butter

Pour it over the dry ingredients, beat until creamy. Add:

1/2 c. buttermilk
2 eggs
1 tsp. baking soda

Bake in jelly roll pan, 11 x 16 x 1 inch at 400 degrees for 18 minutes. Let cool.

ICING:

1/2 c. butter
1/4 c. cocoa
1/3 c. buttermilk

Bring to boil and let cool. Then add:

1 lb. confectioners' sugar
1/2 c. (or more) sm. marshmallows cut in half
1/2 c. chopped nuts
1/2 tbsp. vanilla

Mix well and spread on warm cake.