Toast chiles lightly, turning constantly so not to burn them. When
cool, remove veins and seeds. Cut chiles into small pieces and chop
onion and garlic finely. Mix chiles, onion, and garlic with oil,
vinegar and salt. Let stand for approx 2 hrs. To serve sprinkle with
cheese. (NOTE: This is sometimes called Salsa de tijera (scissors
sauce) since the chiles are usually cut into thin strips with
scissors. When chiles pasilla are used the sauce is called Salsa de
moscas. Salsa de los reyes has three chiles - mulato, ancho, and
pasilla. Good sauce for barbequed meats...)