A rich, deeply spiced curry slow-cooked until the aromatic tomato and onion reduction clings intimately to the tender cuts.
Brown the mutton in the hot mustard oil; remove and set aside.
Fry the onions until deep golden; add the ginger-garlic paste.
Add the coriander, cumin, and chili powders; fry 1 minute.
Return the mutton; add the tomato puree; stir-fry 10 minutes until the oil separates.
Add 1 cup water; cover and simmer 75 minutes until tender.
Uncover and bhunao until the masala coats the meat; sprinkle the garam masala.