Recipe adapted from Tacos: Recipes and Provocations by Alex Stupak and Jordana Rothman
The recipe in Alex Stupak's book calls for pasilla Oaxaqueño chiles, which I was not able to find in the several large Mexican supermarkets I scoured in the Dallas area. I used regular pasilla chiles instead, and the sauce was wonderful. I used it to dress tacos de barbacoa de cordero – lamb barbacoa tacos – as well as some chicken-and-pinto bean tacos made with store-bought roast chicken. If you happen to score some pasilla Oaxaqueños, I'd definitely try those instead. When you slice the onions, if you leave them in whole circles rather than cutting the onion in half through the stem first, they'll hold together better for easier pan-roasting.
Makes about 1 cup.
3-4 medium tomatillos (about 5 ounces total), husked, rinsed and patted dry
2 pasilla chiles
1 garlic clove, skin on
1/2 medium white onion, cut into 1/4-inch thick slices
1 teaspoon salt
1 teaspoon honey
1/4 cup mezcal
1. Heat the broiler or turn your oven to "broil." Place the tomatillos on a baking sheet under the broiler or in the oven until blackened in spots, about 7 minutes. Turn them over and continue to blacken, another 7 minutes. Remove from the broiler and set aside to cool.
2. Remove the stems from the chiles and tear them open. Shake out and discard the seeds. Remove and discard the veins.
3. Set a 12-inch cast-iron skillet over medium heat for 5 minutes. Add the chiles and toast them, turning them a few times, about 45 seconds. Remove the pan from the heat, and transfer the chiles to a bowl. Cover them with boiling water and place a plate over them (weighting it if necessary) to keep them submerged. Let them soak for 30 minutes.
4. Reheat the skillet over medium heat. Add the garlic clove and onion slices and roast, turning them a few times, until softened slightly and blackened in spots, about 6 minutes. Turn off the heat, remove the vegetables from the skillet and set aside to cool. When the garlic is cool enough to handle, pop it out of its skin and discard the skin.
5. Drain the chiles and discard the liquid. Place them in a food processor or blender with the roasted tomatillos, garlic and onion, as well as the salt, honey and mezcal. Process until completely smooth (if you're using a blender, you may need to work in batches). Set a medium-mesh sieve over a bowl and pass the purée through the strainer. Use immediately or store, covered, in the refrigerator for up to one week.