In a large bowl, combine the Bone-In Mutton with whisked Plain Yogurt, Kashmiri Red Chili Powder, Fennel Powder, Dry Ginger Powder and Fine Salt. Mix well to coat the meat, cover and refrigerate to marinate for at least 1 hour (overnight is best).
Heat a heavy-bottomed pot over medium-high heat and add Mustard Oil; warm until it just begins to shimmer. Turn the heat to medium and add a pinch of Asafoetida and the whole spices: Black Cardamom, Green Cardamom, Clove, Cinnamon and Indian Bay Leaf. Fry briefly until the spices are fragrant (about 30–45 seconds).
Add the marinated mutton to the pot in batches if needed, spreading pieces out so they brown evenly. Sear the meat until nicely browned on all sides, stirring and scraping up any browned bits from the bottom of the pan.
Once the meat is browned, pour in enough Water to just cover the mutton, stir gently to combine and bring to a boil. Reduce the heat to low, cover the pot partially and simmer gently until the mutton is tender and the flavors have melded—this may take 1.5–2 hours depending on the cut and size of the pieces.
Occasionally check and stir, adding more water if the curry becomes too dry. When the meat is cooked through and the gravy has reduced to your desired consistency, adjust seasoning with more Fine Salt or a pinch more Kashmiri Red Chili Powder if you like extra color and mild heat.
Finish cooking on low heat until the oil begins to separate slightly from the gravy and the sauce turns glossy. Taste and correct seasoning, then remove from heat.
Serve the Rogan Josh hot with steamed rice, naan or rotis, garnishing simply or leaving traditional flavors to shine.
