Melt together:
1 cup water
1/4 cup cocoa
1/2 lb. margarine

Put in bowl:
2 cups flour
1 cup sugar
salt

Mix in large jug:
1/2 cup buttermilk
1 tsp. baking soda
1 tsp. vinegar
1 tsp. vanilla

Mix all together.  Bake 20 minutes in large pan at 350.  Ice with chocolate butter icing while still warm.