Preheat oven to 350 degrees F (175 degrees C). Grease and flour a 9x13 inch pan.
In a saucepan, combine 1 cup water, 3 tablespoons cocoa, 1/2 cup butter and 1/2 cup shortening. Heat until mixture comes to a boil, then remove from heat.
Add sugar, flour, soda, buttermilk, eggs, cinnamon and vanilla. Mix well and pour into prepared 9x13 inch pan.
Bake at 350 degrees F (175 degrees C) for 30 to 40 minutes or until toothpick inserted in center comes out clean. Have icing ready when cake comes out of oven.
To make the icing: In cleaned out sauce pan from cake, (ALL ABOUT LESS DISHES) combine 3 tablespoons cocoa, 1 teaspoon hot water and 1/2 cup butter or margarine. Melt & mix together. Add confectioners sugar, pecans and milk and mix well. You can add more milk to achieve desired consistency, but too much will make cake soggy.