Preheat oven to 325 degrees. Cream butter and shortening; add sugar and beat until mixture is smooth. Add egg yolks one at a time, beating thoroughly after each addition. Combine flour and soda; add to creamed mixture alternately with buttermilk. Stir in vanilla. Add coconut and chopped pecans. Fold in stiffly beaten egg whites. Pour batter into 3 greased and floured 8 inch cake pans. Bake for 25 minutes or until cake tests done. Cool. ICING: Blend cream cheese and butter until smooth. Add powdered sugar and water, beating until smooth. Add vanilla and blend. Spread between layers and top and sides. Sprinkle top with pecans. NOTE: For more flavor and taste, coconut and pecans may be added between the layers. SOURCE: DIXIE DINING, a recipe collection published by the GFWC : Mississippi Federation of Women's Clubs, Inc. : Contributed by Mrs. R.H. Bell : Typed for you by Nancy Coleman.