The baker’s dos and don’ts for a perfect French Meringue
Sugar: Superfine sugar (or granulated sugar processed in a food processor for a few pulses) is the best to use because the smaller granules lead to easy absorption.
Cornstarch: Cornstarch is an excellent way to foolproof your meringue. Use it to create added fluff and keep your hard-won volume from shrinking.
Cream of Tartar: Often added in when making meringues, acidic cream of tartar provides lift and stabilization.
White Vinegar: This keeps your meringue bright white while being baked.
Egg Whites: In this case, older egg whites are better. Separate the eggs when cold, but allow them to come to room temperature before whipping up.