1 package German's sweet chocolate -- (4-ounce)
1/2 cup boiling water
1 cup butter
2 cups sugar
4 eggs -- separated
1 teaspoon vanilla extract
1/2 teaspoon salt
1 teaspoon baking soda
2 1/2 cups cake flour -- or 2 1/4 cups all-purpose flour *see note
1 cup buttermilk
