1. Prepare the Marinade

1. Toast the coriander seeds in a dry frying pan for 2–3 minutes until fragrant.
2. Place the toasted coriander, rosemary, garlic, chillies, sea salt, black pepper and 1 tablespoon Dark Demerara sugar into a spice grinder or mortar and pestle. Grind until fine.
3. Stir in the olive oil to form a paste.

2. Marinate the Lamb

1. Rub the marinade generously all over the lamb.
2. Place the lamb in a non-metallic dish, cover and refrigerate overnight.

3. Roast the Lamb

1. Remove the lamb from the refrigerator 1 hour before cooking to come to room temperature.
2. Preheat the oven to 180°C.
3. Arrange the onions, garlic halves and thyme in a large roasting tin.
4. Drizzle with olive oil and season with salt and cracked black pepper.
5. Place the lamb on top of the vegetables, fat-side down.
6. Pour the chicken stock around the lamb.
7. Cover loosely with foil and roast for 2½ hours.

4. Caramelise the Onions

1. Remove the foil and carefully turn the lamb over.
2. Toss the onions with the remaining 3 tablespoons Dark Demerara sugar and the balsamic vinegar.
3. Return to the oven, uncovered, and roast for 1 hour.
4. Increase the oven temperature to 220°C and roast for a final 20 minutes, or until the lamb is beautifully browned.

5. Rest the Lamb

1. Transfer the lamb and garlic halves to a serving platter.
2. Cover loosely with foil and allow to rest for 15–20 minutes.

6. Finish the Sauce

1. Place the roasting tin over high heat on the stovetop.
2. Reduce the pan juices until thick and sticky.
3. Season generously with cracked black pepper and adjust salt if needed.

To Serve

• Return the rested lamb to the roasting tin to warm through if desired.
• Spoon over the caramelised onions and pan juices.
• Serve with roasted root vegetables and rosemary roast potatoes.