In a 3-quart saucepan, melt oleo, cocoa and water. Bring to a rapid boil, remove from fire and add sugar, flour, soda and cinnamon. Mix well and add buttermilk, eggs and vanilla. Batter will be thin. Pour into a 15x10x1 -inch pan.
Bake at 325F for 20-25 minutes.
In same saucepan, bring to a boil oleo, cocoa and buttermilk. Remove from heat and add powdered sufarm, vanilla, and cinnamon. Mix well and add 1 cup nuts if desired. Spread over cake.