You’ll Need:1 cup buttermilk 1 teaspoon baking soda 1 cup (2 sticks) margarine 2 cups granulated sugar 3 egg yolks 2 squares unsweetened chocolate, melted 3 cups cake flour 1/2 teaspoon salt 1 teaspoon vanilla extract 3 egg whites, stiffly beatenDirections : Mix buttermilk and baking soda together; let stand