Bring the butter, cocoa and water to a rapid boil and pour over flour and sugar.
Add buttermilk, cinnamon, baking soda and eggs. Beat Well.
Pour this mixture into a buttered or greased and floured 10x15 inch pan.
Bake at 400° for 15 minutes, test to see if the center is still jiggly with a toothpick. (jiggly is a technical term). If it is in fact still jiggly, continue to bake checking to see if the center is fully baked in 5 minute increments.
Remove from the oven and place the pan on a rack to cool.
While your cake is cooling, make your icing.
Bring your butter, cocoa and milk to a boil.
Remove from heat and add remaining ingredients except for pecans.
Beat until smooth, add your pecans and pour over the cake while hot.
Be careful not to over mix the cake or the frosting. The cake won't be as fluffy, and the frosting will be tough.