2 teaspoons kosher salt, divided, plus more as needed
2 to 4 tablespoons neutral oil, such as canola or vegetable
12 (about 5-inch) corn tortillas
2 tablespoons apple cider vinegar
2 tablespoons water
1 tablespoon granulated sugar
2 ounces queso fresco cheese
Instructions
Arrange a rack in the middle of the oven and heat the oven to broil on high.
Prepare the following, adding each to a rimmed baking sheet as you complete it: Peel and quarter 1 medium white onion through the root, then trim off the root. Place 2 wedges on the baking sheet and reserve 1 wedge for serving (reserve the remaining wedges for another use). Remove the papery husks from 1 pound tomatillos, then rinse off the sticky residue. Halve the tomatillos. Trim the stems from 1 medium jalapeño and 1 medium poblano pepper. Remove the seeds from the poblano.
Add 3 peeled garlic cloves. Arrange the ingredients cut-side down in an even layer. Broil for 8 minutes. Flip the peppers, then continue broiling until the tomatillos and peppers are charred in spots, 5 to 7 minutes more. Remove the baking sheet from the oven and set aside to cool slightly, about 10 minutes.
Meanwhile, heat the oven to 350ºF. Shred 2 cups boneless, skinless cooked chicken into bite-sized pieces and season as needed with salt. Grate 4 ounces Oaxaca or mozzarella cheese on the large holes of a box grater (about 1 cup). Place the cheese and 1/2 cup of the Mexican crema in a small bowl and stir to combine.
Very coarsely chop the leaves and tender stems of 1 medium bunch fresh cilantro until you have 1 cup and place in a blender or food processor fitted with the blade attachment. Add the broiled ingredients (reserve the baking sheet), remaining 1/2 cup crema, and 1 1/2 teaspoons of the kosher salt. Blend or process until smooth. Taste and season with more kosher salt as needed.
Wipe the baking sheet clean with a paper towel, then line with more paper towels. Heat 2 tablespoons neutral oil in a small skillet over medium heat until shimmering. Using a pair of tongs, dip 12 corn tortillas, one at a time, into the oil to soften them, about 10 seconds per side (this softens them for easy rolling and keeps them from breaking apart). Add 1 to 2 tablespoons neutral oil to the skillet as needed if the skillet is dry. Place the tortillas on the baking sheet in 2 layers, with more paper towels between the layers.
Assemble the enchiladas: Spread 1/3 of the sauce (about 1 cup) evenly on the bottom of a 9x13-inch baking dish. For each enchilada, place about 2 1/2 tablespoons of the chicken on a tortilla across the lower third; roll it up tightly to enclose the chicken. Place seam-side down in the baking dish against the short side. Place each enchilada snuggly up against the previous one. If you run out of room, place the last few along the bottom of the baking dish.
Pour the remaining sauce over the enchiladas and spread into an even layer. Dollop the cheese and crema mixture evenly over the top.
Bake until the cheese is melted and the sauce is bubbling around the edges (some browning is okay), 30 to 40 minutes. Meanwhile, prepare the toppings.
Trim and thinly slice the remaining jalapeño crosswise into coins. Place in a small, microwave-safe bowl. Add 2 tablespoons water, 2 tablespoons apple cider vinegar, 1 tablespoon granulated sugar, and the remaining 1/2 teaspoon kosher salt. Microwave until the salt and sugar dissolve, about 1 minute. Thinly slice the reserved 1/4 white onion. Crumble 2 ounces queso fresco cheese (about 1/2 cup). Coarsely chop more leaves and tender fresh cilantro stems until you have about 2 tablespoons.
Garnish the enchiladas with the onion, queso fresco, pickled jalapeños (removed from the brine), and cilantro before serving.
