Never Fail (or) Seven-minute Icing

Why I Love This Recipe
My Mom used this icing a lot when I was growing up. Looking through a 1940, Culinary Arts Institute cookbook, I came across it.
Ingredients You'll Need
2 egg whites
1 1/2 cups sugar
1/3 cup water
Few grains salt
1/4 tsp. cream of tartar or 1 1/2 tsp corn syrup
1 tsp. vanilla
Directions
Combine all ingredients except vanilla in the top of a double boiler.
Cook over boiling water, beating constantly with a rotary egg beater.
Cook for 7 minutes, or until mixture holds a point when beater is lifted.
Remove from heat, add vanilla and continue beating until cool enough to spread.
Will frost tops and sides of 2 (9 in.) layers.
Variations:
Lemon - Use lemon juice instead of 2 tbsps. of water, omit cream of tartar and vanilla and add 1/4 tsp. grated lemon rind.
Orange - Use only 1/4 c. of water. Use juice and rind of 1/2 orange instead of vanilla.
Peppermint - Flavor with a few drops of oil of peppermint instead of vanilla, and when frosting on cake is cold but still soft, make a 1- inch border of chocolate flakes around top of cake. Make flakes by scraping bitter choclate with a knife.
Caramel - Use brown sugar in place of granulated
Chocolate - Stir 2 squares of chocolate, melted, into icing just before spreading on cake