Preheat oven 350 degrees F Greased 3 9-inch round cake pans. In small bowl, dissolve baking soda in buttermilk; put aside.In bowl, cream 1/2 c butter, shortening also white sugar to light & fluffy. Stir in eggs, buttermilk mixture, 1 tsp vanilla, 1 cup coconut, baking powder and flour. Stir until just combined.
Pour batter to prepared pans.Bake in preheated oven for 30 to 35 minutes, or until a toothpick inserted in the center of the cake comes out clean. Let cool.
To make the frosting: In a medium bowl, combine cream cheese, 1/2 cup butter, 1 teaspoon vanilla and icing sugar. Beat until light and fluffy. Stir in a small amount of cream to achieve desired consistency. Stir in chopped walnuts and remaining shredded coconut. Spread between layers and over top and sides of cooled cake.
Enjoy!
