Step 1

Combine egg whites through salt: In the bowl of a stand mixer, combine the egg whites, sugar, and salt.

Step 2

Dissolve the sugar into the egg whites: Bring a saucepan with a few inches of water to a simmer. Set the mixer bowl over the simmering water, making sure the water does not touch the bottom of the bowl.Continuously, but gently, stir the mixture until the egg whites are very warm to the touch and the sugar has dissolved, about 4 minutes. Test this by dipping a finger into the mixture and rubbing it between your fingers—the mixture should no longer have any grains of sugar in it and should be very warm to the touch.

Step 3

Beat the meringue: In the bowl of a stand mixer fitted with a whisk attachment, beat the meringue on medium-low speed until foamy, about 2 minutes.Gradually increase the speed and beat until you achieve a stiff peak that droops only slightly when you lift up the whisk, and the bottom and sides of the bowl no longer feel warm to the touch, about 4 minutes. Add the vanilla extract and beat a few seconds to mix it in.

Step 4

Using your Swiss meringue: Swiss meringue is best when used immediately and served the same day. Do not refrigerated it in bulk or it will lose its lightness and become weepy.However, you can frost your cake or cupcakes and refrigerate overnight if needed; the meringue will be less airy the next day, but still fine.