Mix milk and vinegar.
Let stand 5 mintues - this is the buttermilk.
Mix sugar, flour and 4 Tbs. cocoa in a bowl.
In a pan, boil 1 cup water, 1/2 cup margarine and salad oil.
Pour over dry ingredients, mix until creamy.
Add 1/2 buttermilk, eggs and soda; mix.
Bake in large pan 400º for 18 minutes.
15 x 10 inch pan, or a cookie sheet.
Boil 1/2 cup margarine, 1/3 cup buttermilk, and 1/4 cup cocoa.
Remove from heat.
Add 1 box powdered sugar, slowly.
Add 1/2 teasp. vanilla