Preheat your oven to 225°F (110°C) and line a baking sheet with parchment paper.
In a clean mixing bowl, beat the egg whites with an electric mixer until frothy.
Add the cream of tartar and continue beating until soft peaks form.
Gradually add the granulated sugar, one tablespoon at a time, while beating continuously.
Keep beating until the mixture is glossy and stiff peaks form.
Mix in the vanilla extract and cornstarch, if using.
Transfer the meringue to a piping bag fitted with a star tip.
Pipe small mounds onto the prepared baking sheet, leaving space between each.
Bake in the preheated oven for about 1 hour or until the cookies can be lifted easily off the parchment.
Turn off the oven and let the meringues cool inside for about an hour.