Heat the oil in a large frypan and add the onions and a good pinch of salt and fry until soft and golden about 15 minutes.
Then add the mustard seeds and spices and fry for 2 minutes.
Add the sliced potatoes and combine well with the onion and spice mixture. Continue to cook the potatoes and onions over a low heat for 5 minutes turning frequently or until cooked and the onions are a deep golden brown.
Move the potato and onions to one side of the pan or remove completely and add the lamb chops and cook until they reach the desired doneness and are coloured.
Make a paste by combining the tamarind paste and water then squeeze until the paste has been dissolved into the water. Discard the seeds and pulp.
Add the tamarind water/paste to the lamb and potato mixture and mix well to heat through.
Transfer to a serving platter and sprinkle with the chopped mint and green chilli.
