1 Cup (240 ml) egg whites
2 Cups (454 g) sugar
2 Teaspoons (10 ml) vanilla
2 Cups (454 g) Butter (soft but still cool)
1-1/2 Cups (270 g) Crisco or Sweetex
2-2/3 Cups (390 g) powdered sugar
*For chocolate buttercream add 2-3 ounces (57-85 g) melted unsweetened baking chocolate.
Combine fresh egg whites, sugar and vanilla in mixing bowl. Mix lightly over a hot water bath with a whip until mixture reaches 140-160 degrees Farenheit (60-71 degrees Celsius). Place bowl on mixer with whip attachment and beat until stiff peaks form.
Slowly add pieces of butter, followed by shortening. The mixture will fall and look "broken" or curdled. Continue beating and the icing will come together. Stop mixer and add the powdered sugar and beat with whip again for 2-3 minutes until smooth. Scrape bowl often. Add melted and cooled unsweetened chocolate if desired. Keep unused icing refrigerated 2 weeks or freeze.
For fresh egg whites you can use 4 Tablespoons (26g) of powdered egg whites mixed with 3/4 cup (178 ml) of warm water. Add the sugar and vanilla and heat until you can no longer feel granulated sugar and it is completely dissolved. Whip to stiff peaks.
You can substitute butter for the shortening but icing will not be as heat stable.