Mix in large bowl and set aside the two cups of flour and two cups of sugar.
In saucepan, bring 1 stick of margarine, four tablespoons of cocoa, and 1 cup of water to a boil.
Pour boiled mixture over dry ingredients and mix well.
Add 1/2 cup buttermilk (this is what moistens the cake!),1 teaspoons baking soda, 2 eggs, 1 teaspoon vanilla, and 2 teaspoons cinnamon. Mix well.
After mixed, pour into 9 1/2 x 13 1/2 baking pan. Bake 25 minutes @ 400 degrees. As cake comes from oven, pour icing mixture over the top - DO THIS WHILE THE CAKE IS HOT HOT HOT!
Make The Icing!
Boil 4 tablespoons cocoa, 1 stick (1 cup)margarine, and 6 tablespoons of milk together for 1 minute. Add to powdered sugar and vanilla. Blend/stir until the lumps are gone, and pour over HOT cake. Let sit for 30 minutes until cool.