Cream margarine, shortening, and sugar. Add egg yolks and beat. Add flour and soda, alternating with buttermilk. Add vanilla, coconut and chopped nuts. Fold in stiffly beaten egg whites. pour into 2 greased and floured 8-inch cake pans. Bake at 350 degrees for 25 minutes.
Cream Cheese Frosting:
Beat until smooth; ice cooled cake.