Mix the lamb cubes in a bowl with the ginger, garlic, garam masala, chilli powder, turmeric, chilli, coriander and mint. Cover and marinate in the fridge overnight.
Wash the rice in a sieve under cold, running water until the water from the rice runs clear. Put the sliced onion in a sieve, sprinkle with the salt and leave for 10 minutes to drain off any liquid that oozes out. Rinse and pat dry.
Heat the oil and butter in a large, heavy-based saucepan, add the onion and fry for about 10 minutes or until golden brown. Drain through a sieve, reserving the oil and butter.
Remove the lamb from the marinade, reserving the marinade, and fry in batches in a little of the oil and butter until the lamb is well browned all over. Transfer to a ‘degchi’ (thick-based pot) or heavy casserole and add the browned onion, any remaining marinade and the yoghurt, and cook everything over low heat for 30-40 minutes, or until the lamb is tender.
In a separate saucepan, boil enough water to cover the rice. Add the rice to the pan. Return the water to the boil, cook the rice for 5 minutes, then drain well and spread the rice evenly over the meat. Pour
To make the sealing dough,