Bring 1 inch of water to a simmer in a medium saucepan. Combine egg whites, corn syrup, sugar and salt in a metal bowl large enough to sit on top of the saucepan. Whisk constantly in bowl over water until sugar is dissolved and
eggs have reached 160°, about 3 to 5 minutes (do not overcook, as the eggs could scramble). Pour mixture and
vanilla into the bowl of a stand mixer fitted with a whisk and beat on high speed until fluffy, about 5 minutes. Set aside.