While most authentic recipes call for primarily tomatoes, I chose this version with solely tomatillos. It was delicious. Very complex flavors with a bit of heat.
1 pound fresh tomatillos
1 large poblano pepper (about 2 1/2 to 3 ounces), seeded and cut into 4 pieces
2 tablespoons olive oil
1/2 cup raw unsalted pumpkin seeds
2 whole allspice
1/2 teaspoon whole cumin seed
1 medium onion, chopped
4 cloves garlic, minced
1 cup chopped fresh cilantro leaves, plus 1/4 cup for garnish
1 cup low‑sodium chicken broth
1 medium (2‑inch) jalapeño pepper, seeded and roughly chopped
1/2 teaspoon salt
4 (6‑ounce) boneless skinless chicken breast halves, pounded to 1/2‑inch thickness
Preheat the broiler. Remove papery outer layer from tomatillos then rinse them in warm water to remove some of their natural stickiness. Pat dry, then cut into quarters. Toss tomatillos and poblano with 2 teaspoons of the oil, place on a baking sheet and broil until charred, about 10 minutes.
Heat a large sauté pan over medium heat. Add pumpkin seeds, peppercorns, allspice, and cumin and toast until pumpkin seeds are fragrant, 3 to 4 minutes. Transfer to a plate. In same sauté pan, heat 2 teaspoons oil over medium heat. Add onions and cook until soft and translucent, about 5 minutes, add the garlic and cook for 1 minute more.
Place tomatillos, poblano, onions and garlic, cilantro, chicken broth, jalapeño, toasted seeds and spices and salt in a blender and blend on high until totally smooth, about 30 seconds.
Heat the remaining 2 teaspoons olive oil in skillet and cook the chicken until browned on both sides and nearly cooked through, about 5 minutes per side. Add Pepián sauce to skillet, covering chicken pieces. Bring to a simmer and cook an additional 3 to 5 minutes, until chicken is cooked through. Serve chicken topped with sauce and garnished with cilantro and lime wedges.