Marshmallow Frosting for Angel Food Cake

This is the BEST ever frosting and I have it on my birthday cake every year. I love it.

1 1/2 cups sugar
1/2 teaspoon salt
Whites of 3 eggs
1/2 cup water
6 marshmallows
1 teaspoon vanilla

Boil sugar and water without stirring until the syrup spins a thread (meaning it kind of makes a line if you lift it up, not all drippy..) ; melt marshmallows in this syrup. Pour slowly over stiffly beaten whites of eggs, beating constantly; add flavoring and spread very thickly over layers.