Heat the oil in a large saucepan and fry the chicken pieces all over until the pores are closed and the chicken pieces are golden yellow. Take out the meat, add the onions, garlic, chilli and spices to the saucepan and let simmer for 2 minutes over a low heat, stirring frequently. Stir in tomatoes, water, mint and chickpeas, return the meat to the saucepan and season with salt. Cover the pot with a lid and simmer for about 20 minutes, until the chicken is tender and through. Try and season if necessary, then sprinkle with chopped coriander and optionally drizzle with yoghurt.