- 1/2 lb fresh tomatillos, husks discarded and tomatillos rinsed and quartered
- 3 fresh green serrano chiles, coarsely chopped (including seeds)
- 1/4 cup chopped white onion
- 3 garlic cloves, quartered
- 3/4 teaspoon salt, or to taste
- 1/2 cup water
- 2 tablespoons vegetable oil
- 3 tablespoons finely chopped fresh cilantro
- 1 to 2 tablespoons vegetable oil
- 12 (4-inch) corn tortillas (see cooks' note, below)
- 1 cup shredded cooked chicken (from 1 chicken breast half)
- 2 to 3 tablespoons crema or crème fraîche
- 1/3 cup finely chopped white onion
- 1/3 cup finely crumbled queso fresco (Mexican fresh cheese)
- Purée tomatillos, chiles, onion, garlic, salt, and water in a blender until smooth.
- Heat oil in a 10-inch heavy skillet over moderate heat until hot but not smoking, then carefully add tomatillo purée (oil will splatter) and simmer, stirring, until thickened, 8 to 10 minutes. Stir in cilantro and simmer 1 minute. Transfer to a small bowl.
- Put oven rack in middle position and preheat oven to 200°F.
- Heat 1 tablespoon oil in cleaned dried skillet over moderate heat until hot but not smoking, then briefly cook tortillas, 3 at a time, until softened and hot but still pale, about 10 seconds per side, adding more oil if necessary. Transfer tortillas with tongs to paper towels to drain briefly, then to a large shallow baking pan in oven to keep warm, arranging tortillas in one layer (overlapping slightly if necessary) and covering pan with foil.
- Spread each warm tortilla with about 1 teaspoon salsa, then top sparingly with a few shreds of chicken. Thin crema with a little water and drizzle over chicken, then sprinkle with onion and cheese. Serve immediately.