In a large bowl, cream the butter, shortening and sugar until light and fluffy. Beat in egg yolks and vanilla. Combine flour and baking soda; add to creamed mixture alternately with buttermilk. Beat just until combined. Stir in coconut and pecans.
In a small bowl, beat egg whites until stiff peaks form. Fold a fourth of the egg whites into batter, then fold in remaining whites. Pour into three greased and floured 9-in. round baking pans.
Bake at 350° for 20-25 minutes or until a toothpick inserted near the center comes out clean. Cool for 10 minutes before removing from pans to wire racks to cool completely.
In a large bowl, beat cream cheese and butter until smooth. Beat in confectioners’ sugar and vanilla until fluffy. Stir in pecans. Spread frosting between layers and over top and sides of cake. Store in the refrigerator.