Cook the meat: In a large pot, combine chicken, water, salt, onion, and garlic. Bring to a boil, skim off foam, reduce heat, and simmer for 30–40 minutes. Reserve the broth and remove the chicken.
Toast the seeds: In a dry skillet, toast the pumpkin seeds over medium heat until they puff and pop, about 3–5 minutes. Be careful not to burn them.
Blend the sauce: In a blender, combine toasted seeds, hoja santa, epazote, poblano, serranos, tomatillos, onion, garlic, and about 2 cups of the reserved broth. Blend until smooth.
Cook the sauce: In a large cazuela or pot, heat lard or oil. Pour in the green sauce and stir constantly for 5–7 minutes until thickened and darkened slightly.
Combine and simmer: Add the chicken and about 2 more cups of broth. Stir to coat, cover, and simmer for 25–30 minutes until the flavors meld.
Serve hot: Ladle into bowls and serve with white rice and warm corn tortillas.
What to Serve With It
Sides: Steamed white rice, chayote sautéed with onions, or tamales de masa colada
Drinks: Agua de guanábana or a cold horchata
Bread: Tortillas, always — preferably soft and warm from a comal