Wash and soak the rice for 20 minutes in cold water. Mix all the ingredients for the marinade together, spread over the chicken thighs and set aside for 15–30 minutes. Meanwhile, soak the saffron in the milk for three to five minutes, then mix in the ghee and rosewater.In a large casserole simmer the chicken for about 20 minutes until tender (add half a cup of water if it seems too dry). Slice the onions and shallow fry in some oil until brown, drain. Bring the whole spices and salt to the boil in 1.5 litres of water, reduce the heat and simmer for five minutes or so. Add the drained rice and boil for about eight to nine minutes – the rice should be 80–85 per cent cooked. Drain the rice and put it over the marinated cooked chicken.Sprinkle the reserved handful of chopped mint and the soaked saffron mix over the rice and cover the casserole with a lid. Heat the biryani on a low flame for five to seven minutes and remove. Sorinkle the fried onions on top before serving. Leave it to rest for five minutes and serve with a raita of your choice.