This is one of the most common table sauces in the state. It gets its haunting flavor from the Oaxacan pasilla chile, a smoked and dried type not to be confused with the regular Mexican pasillas that come from a different chile and are dried without smoking. Once unavailable in the U.S., the Oaxacan pasillas are starting to be imported by a few distributors. If you can’t find them, dried chipotles or morita chiles are the closest substitute.
The sauce would go with any Oaxacan meal.