Step 1

Combine yoghurt, ginger, garlic, spices and lime juice in a bowl and season to taste. Slash lamb at intervals, rub all over with yoghurt mixture and into the incisions, then wrap in plastic wrap and refrigerate overnight to marinate.

Step 2

Unwrap lamb, place in a roasting pan and bring to room temperature (1-1½ hours). Preheat oven to 120C. Meanwhile, heat ghee in a frying pan over medium-high heat, add onion and fry, stirring occasionally, until crisp and golden brown (8-10 minutes). Season to taste, cool briefly, then scatter onion over lamb. Add 500ml water to roasting pan, cover with foil and roast until meat is fall-apart tender (11-12 hours). Pour pan juices into a jug, skim off excess fat and season to taste.

Step 3

For saffron pilaf, heat ghee in a large saucepan over medium-high heat, add onion and garlic and sauté until tender and translucent (5-6 minutes). Stir in rice to coat, then add stock, saffron and its soaking liquid and 250ml hot water. Season to taste, bring to the boil, cover with a tight-fitting lid, then reduce heat to low and cook without uncovering for 15 minutes. Remove from heat, stand without uncovering for 5 minutes, then uncover and fluff up with a fork.

Step 4

For mint yoghurt, process ingredients in a food processor and season to taste.

Step 5

Pile pilaf onto a platter, top with lamb, scatter with coriander, mint and green chilli, and serve with pan juices, mint yoghurt and lime wedges.