Put the remaining mixture on top, cover and cook over low heat for 10 minutes. Turn onto a plate and return to the pan with the unroasted side down and cook for another 10 minutes. For tortillas (as well as frittatas and many other dishes), it is very convenient to use a double mold. The cooking time may vary depending on which type of tortilla you like – wetter (cook less) or drier (cook longer). The tortilla is delicious and cold, so it is convenient to cook it the day before and take it with you on a picnic.