How to Make It
In a large stainless-steel bowl, combine the egg whites with the sugar, water and salt. Set the bowl over a saucepan filled with 2 inches of boiling water and beat the egg whites at high speed until stiff and glossy, about 7 minutes. Remove the bowl from the heat, add the vanilla and continue to beat at high speed until the frosting is cool to the touch, about 8 minutes longer. Use the frosting immediately.