In a large bowl combine yogurt, 2 tbs garlic paste, 1 tbs ginger paste and 1.5 tsp salt. Add the lamb pieces and mix thoroughly so each piece is coated. Cover and refrigerate for at least 2 hours, preferably overnight for best tenderness and flavor.

Spice Paste & Aromatics

Prepare whole spices and onions

Heat oil and butter together in a heavy-bottomed Dutch oven or deep pan over medium heat until shimmering. Add crushed green cardamom, cloves, black cardamom, cinnamon stick and bay leaves. Fry for 30–45 seconds until fragrant, being careful not to burn.

Caramelize onions

Add the thinly sliced onions and a pinch of salt. Cook, stirring frequently, on medium-low heat for 12–18 minutes until the onions are deep golden and caramelized. If onions brown too quickly reduce the heat; you want sweet, deeply colored onion to form the curry base.

Build the spice paste

Stir in the additional 1 tbs garlic paste and 1 tbs ginger paste, cooking 1 minute to remove raw aroma. Mix in the tomato paste and cook 2–3 minutes until it darkens slightly. Add Kashmiri chili, ground coriander, ground cumin, ground fennel (if using) and turmeric; cook another 1–2 minutes, stirring, to bloom the spices.

Brown the lamb

Increase heat to medium-high. Add the marinated lamb (including any remaining marinade) in batches to avoid crowding. Brown the pieces on all sides for 4–6 minutes per batch. Return all browned lamb to the pot.

Deglaze and simmer

Pour in 500 ml water or stock, scraping any browned bits from the bottom. Add 1 tsp salt (adjust later). Bring to a gentle boil, then reduce heat to low, cover partially, and simmer gently for 1 hour 30 minutes to 1 hour 45 minutes, or until lamb is tender and falling from the bone. Stir occasionally and skim any foam or excess oil from the surface.

Finishing & Garnish

Concentrate sauce and finish

Uncover for the last 20–25 minutes of cooking to reduce and thicken the gravy to your preferred consistency. If the sauce reduces too much before lamb is tender, add a few tablespoons of hot water. Once lamb is tender and sauce coats a spoon, stir in 1 tsp garam masala and crushed kasoori methi. Cook 2–3 minutes to integrate flavors.

Adjust seasoning and garnish

Turn off heat. Stir in 1 tbs lemon juice and chopped cilantro. Taste and adjust salt or acidity as needed. If using, add slit green chilies on top for heat. Let rest 10 minutes before serving to let flavors meld.

Serve

Serve hot with steamed basmati rice, jeera rice, or warm naan. Spoon generous gravy over rice and garnish with additional cilantro if desired.