Edelweiss White Cake

Name: Edelweiss White Cake
Ingredients: 4 1/2 cups butter, at room temperature, plus more for greasing; 3/4 cups milk, at room temperature; 1/4 cup sour cream, at room temperature; 2 teaspoons almond extract; 1 teaspoon vanilla extract; 6 egg whites, at room temperature; 2 1/4 cups white cake flour; 1 3/4 cups sugar; 4 teaspoons baking powder; 1 teaspoon salt; Black Sheep Crusting Buttercream, recipe follows; 5 cups high-ratio shortening; 3/4 cup very hot coffee creamer; 5 pounds confectioner's sugar