For the duck seasoning:
Remove any excess fat from the mutton and cut up any large pieces. Set it aside.
Using a large pan over a medium heat, dry roast the cumin seeds until the scent rises, then add the onions and ghee. Sweat the onions to soften them, stirring from time to time. Make a paste with the turmeric, paprika, garam masala, chilli powder and a little water. Add this to the onions and allow it to cook out for a few minutes. Add the mutton, grated garlic and ginger, and the piece of cinnamon stick and mix everything together.
Chop the pineapple and the chilli very finely together until they are almost puréed and add them to the pan. Then add the chopped tomatoes, tomato purée, Maldon salt and pepper and stir them in. Mix together the vinegar and jaggery or Demerara sugar and add those to the pan too. Stir everything thoroughly, and add the water.
Bring to the boil, remove any scum and reduce the heat. Allow the curry to simmer gently until the mutton is tender – how long this takes will depend on the size of the pieces, but allow at least 90 minutes to 2 hours. During cooking, check the curry every so often and add a little more water if necessary. Check the seasoning.
Serve with steamed Basmati rice, perhaps a vegetable curry, naan bread, sambals, chutneys and raita...