The thin, finely layered pastry dough known as phyllo is essential to Greek cooking, used to make all sorts of savory pies, casseroles, and desserts. You can make your own from scratch (see Making Hortopita
), but there are many good-quality premade phyllo doughs available. Store-bought versions come frozen in a number of styles and thicknesses—sometimes indicated by a number grade—each suited to a different kind of preparation. Below, a quick guide.