Cake: Mix the flour and sugar together in a large bowl, set aside.
In a sauce pan, add butter, shortening, cocoa and water, bring these to a rapid boil and pour over the flour and sugar mixture, stir well. Then add buttermilk, mix well. Add eggs, baking soda and vanilla and mix together.
Pour in a cake pan and bake for 20 minutes at 400 degrees F. Check with a toothpick, when toothpick comes out clean it is done.
Icing: Melt butter, cocoa and milk together and bring to a boil. Remove from heat and add powdered sugar, vanilla and pecans. Beat well and pour over Hot cake.