Seven-Minute Frosting

Apparatus:

Whisk
Large stainless-steel bowl
Instant-read thermometer
Wide, deep skillet

Components:

5 tablespoons water
1/4 teaspoon cream of tartar
1 1/3 cups sugar
2 large eggs whites at room temperature
1 tablespoon light corn syrup
1 teaspoon vanilla
1/2 to 1 cup chopped nuts or shredded sweetened dried coconut (optional)

Procedure:

1. Whisk water, cream of tarter, sugar, egg whites, and corn syrup together in a large, stainless-steel bowl.
2. Set the bowl in a wide, deep skillet filled with simmering water (about 1 inch, water level is at least as high as the depth of the egg whites in the bowl).
3. Beat the whites on low speed until the mixture reaches 140 degrees F on an instant-read thermometer. Do not stop beating while the bowl is in the skillet, or the egg whites will be overcooked. If you cannot hold the thermometer stem in the egg whites while continuing to beat, remove the bowl from the skillet to read the thermometer, returning the bowl to the skillet to continue.
4. Beat on high speed for exactly five minutes.
5. Remove the bowl from the skillet and add vanilla, beating on high speed for two to three more minutes to cool.
6. Stir in coconut or nuts, if you are using them.
7. Use this frosting the day it is made.

Original recipe from:

Seven-Minute Frosting
Adapted from Joy of Cooking
http://smittenkitchen.com/2007/09/layered-lemon-love/

...which had lemon cake, the filling and this frosting