The simplest, most common or classic type of meringue is the French
meringue. It’s made by beating egg whites until frothy or soft peaks
form (they’ll barely hold their shape), then adding the sugar
gradually to make sure it dissolves, while continuing to whip the
whites. Once all the sugar has been added, you’ll whip the meringue to
stiff peaks (they stand up and stay in place when the beater is
lifted), or as determined by your recipe. French meringue is the least
stable but lightest of the three. Sometimes it’s poached or folded
into batters for cakes or soufflés, etc. But typically this type is
spooned or piped into cookies, Pavlova, or a desired shape, and baked
low and slow. Once baked it becomes crisp yet airy and shouldn’t be
brown.
The sturdiest of the three types, Italian meringue is a cooked
meringue. Use a candy thermometer to track the temperature as the egg
whites cook. It involves making a sugar syrup (sugar and water) cooked
to the soft-ball stage (238–240°), and slowly adding it to whipped egg
whites, with the mixer running, until stiff, glossy peaks form and the
meringue feels cool to the touch. It’s considered the most challenging
to make because it not only involves the syrup, but the syrup must be
ready at the same time as the whites. Thus, this may require raising
or lowering the heat of the syrup and/or the speed of the stand mixer.
Italian meringue should have a soft and creamy texture — they’re
usually used for buttercream or meringue frostings or for decorating
pastries.
Swiss meringue is a gently cooked meringue — the egg whites and sugar
are (continually) whisked together and heated over a double-boiler
until the sugar dissolves, the mixture starts to thicken, and it
reaches about 130° on a candy thermometer (or as determined by your
recipe). It’s then beaten, right away, off heat, until stiff, glossy
peaks form and it feels cool to the touch. It’s softer yet denser in
texture than French meringue and is often used as a base for
buttercream frostings, cookies, or Pavlova. Of the three types, this
is considered the middle of the road in terms of stability.