1. Using a pestle & mortar grind together the black peppercorns, coriander seeds, cumin seeds, fennel seeds and green cardamom pods.
2. Mix in the cinnamon powder and turmeric powder, garlic paste and most of the olive oil.
3. Rub the spice paste all over the lamb making sure you rub it into all the holes.
4. Fill the holes with sliced chilli, rosemary, sliced garlic and whole cloves.
5. Cover and leave to marinate in the fridge for at least a few hours, but overnight would be ideal.
6. Bring the lamb back to room temperature before cooking. Preheat the oven to 160°C/300°F/gas 2.
7. In a deep roasting tin lay the sliced onions and whole garlic cloves on the bottom and place the lamb on top. Sprinkle with sea salt and drizzle with the remaining olive oil.
8. Slow cook in the oven for 30 minutes before pouring in the stock or water into the tray.
9. Cook for another 3 hours, basting the meat with the juices every half an hour.
10. Leave to rest for around 15 minutes before carving and serving with the caramelised onion jus from the tray. Simply delicious!