Fancy Black Walnut Cake

Cake Ingredients:
½ cup butter, softened
½ cup shortening
2 cups sugar
5 eggs, separated
1 cup buttermilk
1 teaspoon baking soda
2 cups all-purpose flour
1 teaspoon vanilla
1 ½ cups Black Walnuts
1–3 ounces flaked coconut
½ teaspoon cream of tartar
Frosting Ingredients:
1 package (8 ounces) cream cheese, softened
1 stick (½ cup) butter, room temperature
1 teaspoon vanilla
1 box (4 cups) powdered sugar
1 cup ground Black Walnuts