Pat chicken dry with paper towels; do not rinse it. Season with half the salt and the pepper. Heat oil in a large skillet over medium-high heat. Brown chicken skin-side down for 6–8 minutes, then turn and brown for 2 minutes. Lower heat if the pan smokes.

Add 1 cup of the broth around the chicken, bring to a gentle simmer, cover and cook over medium-low heat for 25–35 minutes. Check the thickest part away from bone: it must reach at least 165°F (74°C). Thighs may become more tender around 175–180°F. Add a splash of broth if the pan gets dry.

While the chicken cooks, toast pepitas in a dry skillet over medium-low heat for 3–5 minutes, stirring often, until fragrant and beginning to puff. Do not let them darken. Transfer to a plate and reserve 1 tablespoon for garnish.

Put tomatillos, onion, garlic and jalapeño in a saucepan with water just to cover. Simmer 8–10 minutes, until tomatillos soften but do not disintegrate. Drain. Let cool until safe for your blender; never seal steaming-hot liquid in a blender.

Blend the remaining toasted seeds with the remaining 1 cup broth, softened vegetables, cilantro, romaine and remaining salt until as smooth as your blender allows. Work in batches and follow the blender manufacturer's warm-liquid instructions.

Transfer the fully cooked chicken to a clean plate. Pour the green sauce into the skillet with the cooking juices. Simmer gently, stirring frequently, for 8–10 minutes until spoonable; add broth a tablespoon at a time if thick. Return chicken and warm through for about 3 minutes, keeping it at least 165°F. Taste before adding the lime juice; use only as much as needed.

Divide chicken and sauce among four plates. Scatter the reserved pepitas on top. Serve optional rice or tortillas separately.