At room temperature, egg whites whip more easily and produce a meringue that is more stable.
Sugar dissolves entirely when added gradually, avoiding a grainy texture.
In order to ensure that the meringue maintains its shape during baking, check for firm peaks by whisking the egg whites until glossy, stiff peaks form.
To prevent the meringue from becoming deflated, fold in the cornstarch and vinegar very gently.
To get a crisp outside without browning, bake at a low temperature for an extended period of time.