I've been a fan of Dan Toombs - The Curry Guy - for a few years now, and we've been trying to get this collaboration together for about a year. So, it finally happened, and Dan came and showed me how to cook a few things. This is his recipe for Railway Mutton Curry - the story goes this is a curry that was served on railways during the Raj, toned down for British tastes.
You don't have to pre-cook these things, it just makes the final assembly of the curry go faster. If you choose to cook the meat in the sauce, add the meat cooking time to the overall time for the curry.
Now add the broth that the lamb was cooked in. If your lamb is cold and the broth has set like jelly, just warm it gently until it melts. If you're cooking the meat in the sauce from raw, add 1 or 2 cups of water. Add the meat and the drained potatoes. Stir well, then add the tamarind, coconut milk and yoghurt. cook gently for 5 minutes, then add a pinch of salt, finely chopped coriander, and the dried methi crumbled between your fingers. Serve with rice, naan, the usual suspects.