White Mountain Frosting

1. Stir sugar, water, and cream of tartar together in a saucepan over medium heat. Cover and bring to a boil, then uncover and cook until a candy thermometer reaches 238 degrees F (115 degrees C), 5 to 7 minutes; syrup should spin a long thread when dripped from a spoon.

2. While the syrup is cooking, beat egg whites in the bowl of a stand mixer with the whisk attachment until stiff peaks form.

3. When the syrup has reached temperature, slowly pour a thin stream into egg whites, beating constantly, until frosting stands in peaks. Stir in vanilla and salt.

Tips

You can use any flavor extract instead of vanilla.