1. Combine the ginger-garlic paste with salt and red chilli powder and rub into the mutton.
2. Add vinegar and spring onions, leave to marinate for ½ an hour.
3. Place the mutton in an oven-proof dish, pour water over it until 3/4th of the meat is covered with water.
4. Cover tightly with aluminium foil and cook in pre-heated oven (300°F).
5. Cook for 1 hour approximately.
6. Keep checking, do not overcook the mutton.
7. Remove the foil, leave to cool.
8. Remove the mutton, strain and reserve the liquid.

For the gravy:

1. Roast the peppercorns on a tawa, crush coarsely and set aside.
2. In a heavy bottomed pan add the reserved liquid and bring to a boil.
3. Add tomato puree, reduce heat.
4. Simmer on low heat until gravy thickens.
5. Add pepper, chives, garam masala and salt to taste.
6. Cook on low heat for 2-4 mins.
7. Add butter and stir-cook until the butter melts and is well mixed into the gravy.
8. Remove from heat, add cream and half of the blackcurrant juice.
9. Mix well. Adjust the salt.
10. Arrange the mutton in an ovenproof dish.
11. Sprinkle the remaining blackcurrant juice on the mutton and heat it for 3-4 mins. in the pre-heated oven.
12. Remove the mutton dish from the oven and pour the gravy over it.
13. Sprinkle some extra freshly ground pepper and chopped spring onions over it. Serve hot.