Drain the chickpeas, rinse under cold running water and drain again. Place them in a saucepan, cover with 5 cm (2 inches) of water and bring to the boil. Boil rapidly for 10 minutes, then lower the heat and simmer, partially covered, until tender, adding more water as necessary. This will take anything up to 1¾ hours. Drain the chickpeas and set aside.
Place the chicken breasts, stock and water in a second saucepan. Bring to the boil, lower the heat, cover the pan and simmer for 10–15 minutes or until the chicken is just cooked. Remove the chicken from the stock, place it on a board and shred it, discarding the skin.
Set the shredded chicken aside. Add the chickpeas, tomatoes, saffron (if using), onions, rice and lentils to the stock remaining in the pan. Cover the pan and simmer for 30–35 minutes or until the rice and lentils are tender.
Add the shredded chicken, coriander and parsley just before serving. Heat the soup for a further 5 minutes without letting it boil. Season to taste and serve the soup, garnished with drizzles of natural yogurt and coriander sprigs.