- 2 ounces pasilla chiles (6), wiped clean, stemmed, slit open, seeded, and deveined
- 2 ounces guajillo chiles (8), wiped clean, stemmed, slit open, seeded, and deveined
- 1/4 cup distilled white vinegar
- 1/4 cup light Mexican beer
- 1/2 cup chopped white onion
- 4 garlic cloves, peeled
- 1 teaspoon fine salt, or 2 teaspoons kosher salt
- 1/2 teaspoon dried oregano, preferably Mexican
- 1/4 teaspoon cumin seeds
- 5 whole cloves
- 2 pounds skirt steak, cut into four 8- to 9-inch pieces
- 1 teaspoon fine salt, or 2 teaspoons kosher salt
- 1/2 cup pasilla-guajillo adobo (above)
- About 1 tablespoon mild olive oil or vegetable oil
- Heat a comal, griddle, or heavy skillet over medium-low heat, and toast the chiles 2 or 3 at a time, turning them over and pressing down on them with tongs frequently, until the chiles are fragrant, about 1 minute per batch. Soak the chiles in enough cold water to cover until they're soft, about 30 minutes. Drain and discard the soaking water.
- Put the vinegar and beer in the blender jar with the chiles and the remaining adobo ingredients. Blend until smooth, at least 3 minutes, adding a little water if necessary to puree. If you like a silky, smooth texture, strain the adobo through a medium-mesh sieve. Set aside 1/2 cup of the adobo to marinate the steak, and keep the rest in an airtight container in the refrigerator for up to five days or in the freezer for up to one month.
- Pat the steaks dry, season them with the salt, then coat them generously with adobo. Let them marinate in the refrigerator for 1 to 2 hours.
- Heat a grill or grill pan over medium-high heat. Lightly oil the grill or grill pan and cook the steaks, 3 to 5 minutes on each side for medium-rare, depending on their thickness. Let the steaks rest for 5 minutes before slicing for tacos or serving as whole steaks.