Use this frosting to make our Coconut Layer Cake. If the weather is humid, beat the icing for an additional minute in each step to help stiffen it.
Combine egg whites, sugar, corn syrup, and cream of tartar with 5 tablespoons cold water in top of a double boiler. Fill bottom of double boiler with two to three inches water; top pan should not touch water. With water boiling vigorously, beat egg mixture using a hand mixer on medium low 4 minutes, then high 3 to 4 minutes. Remove from heat. Add vanilla; continue to beat until icing holds its peaks, 3 to 5 minutes more; do not overmix or icing can get grainy.