Although the basic recipe has changed little in the 400 years or so since these humble components first came together, it has been refined in three slightly different ways to create French, Swiss, and Italian interpretations.
The easiest and most basic approach to meringue is adding sugar to whipped egg whites, one tablespoon at a time, until the perfect equilibrium of thick, smooth, and glossy is achieved.
The ethereal texture that results is the inspiration for many a delicate dessert. This meringue can be shaped any which way: scooped into elegant ovals and poached to form silken, fanciful "floating islands"; spread atop pies and baked until browned; or piped into rounds and baked until slightly chewy or crisp throughout to create featherweight macaroons and dacquoises, waiting to be layered with frosting, custard, fruit, or whatever the cook may fancy.
Beat the egg whites until they're foamy and smooth before you begin to add the sugar. (If the egg-white foam appears dry, you've beaten the whites too long, and the resulting meringue will not rise properly. You should start over with a new batch.)
To avoid a granular texture, add the sugar to the foam gradually. This lends the meringue stability. After all the sugar is incorporated into the egg whites, beat the mixture until stiff peaks form. They will stand up and stay in place when the beater is lifted.
Be careful not to overbeat the mixture. The meringue should be smooth, glossy, and flexible, not dry or grainy. Because raw eggs are used and the mixture isn't heated, this version of meringue must be cooked.
This intermediate-level meringue is achieved by whisking egg whites and sugar over simmering water until the sugar has dissolved completely, and then removing it from the heat and beating it slowly until cool and firm. It's far more stable than its French counterpart, yet not as hardy as Italian meringue. It brings a silken smoothness to buttercream, but one of its most stunning incarnations is the pavlova -- a winsome, swooping shell that's baked until firm to the touch though still compellingly chewy within.
The simmering water should not touch the bottom of the bowl of egg whites as it may overheat them, affecting the protein structure and resulting in a less-than-optimal texture. The best way to determine if the sugar has dissolved is to rub a little of the mixture between your fingertips; it should feel smooth, not gritty. Finished Swiss meringue will be far glossier than French meringue.
This sturdy meringue is formed by heating a sugar syrup until it reaches the soft-ball stage. The syrup is added slowly to softly beaten egg whites, and then the mixture is beaten vigorously until stiff, glossy peaks form. Although overbeaten French and Swiss meringues will lose their ability to peak when piped, Italian meringue is far more forgiving. The least fragile meringue, it brings sturdiness to mousses and semifreddi and is also harnessed for such grand applications as baked Alaskas (large and small). Italian meringue's unwavering stability allows the resulting desserts to be finished in the oven, frozen, or torched to dramatic effect.
Pour the hot sugar syrup slowly and steadily into the mixer bowl. Do not pour it directly onto the beater attachment or it will spatter.