Rub the chicken pieces with the turmeric and salt. Set aside.
Heat the oil in a large frypan over medium heat. Fry the poppy seeds, peppercorns, fennel seed, coriander seed, and cumin seed in the hot oil until they just begin to change colour; remove from the frypan, keeping the oil in the frypan. Grind the spice mixture with a mortar and pestle and set aside.
Add the onion, green chillies, curry leaves, ginger paste, and garlic paste to the remaining oil; cook until the onions are golden brown, 7 to 10 minutes. Stir the tomatoes and ground spices into the mixture; cook until the tomatoes are softened. Add the chicken. Season with salt and simmer for 5 minutes. Pour the water over the mixture, cover, and cook until the chicken is no longer pink in the middle and the juices run clear, about 30 minutes. Serve hot.