Pour the oil into a wide non stick lidded pan and set over a medium high heat. When hot add the mustard seeds, chillies and urad dal.
As soon as the mustard seeds start to pop and the dal reddens add the shallots, garlic and curry leaves. Stir and fry for 3 minutes or until the onions just start to take on some colour. Add the ginger and stir a few times.
Stir in the tomatoes and cook for 2 minutes. Add the lamb and the turmeric and stir and cook for a minute. Add 475ml water and the salt. Bring to a boil, cover, reduce heat to low and cook gently for about an hour, until the meat is tender.
Remove the lid, increase the heat to high and boil away some of the liquid until you are left with a thick sauce clinging to the meat.