Bring about an inch of water in a saucepan to a simmer. Combine the egg whites and sugar in the bowl of a stand mixer. Place the bowl over the simmering water and stir the egg mixture with a rubber spatula until it is hot and all of the sugar has dissolved, about 5 minutes.
Remove from heat and place the bowl onto the stand mixer, fit with a whisk attachment. Beat on high speed until very thick, glossy and stiff peaks when you lift the beater. Add the vanilla, mix well.