The size of the baking / casserole dish is important. The lamb should fit snugly into the container with about 2cm between the edge of the lamb and the container. If the dish is too big the water will evaporate and the lamb can dry out. It may also take longer to cook.

Cut the onions and slice them thickly. Lay them in the bottom of your baking dish or casserole dish. 

Place all the marinade ingredients into a food processor and blitz until it forms a smooth paste.

Pour the marinade over the lamb and make sure the piece of lamb is fully covered with the marinade. If there’s any left over just pour it on top of the lamb. Place the lamb in the fridge for a couple of hours or overnight.

Heat the oven to 170º celsius. 

Add one cup of water to the baking casserole dish. Cover with the lid and place it in the oven for a total of 4 hours. If you are using a baking dish that does not have a lid, simply use aluminum foil to act like a sealed lid. Make sure there are no holes in the foil.

At 2.5 hours remove the lid/foil, check there is liquid still pooling at the bottom of the baking casserole dish. Use the liquid to baste the top of the lamb. If the liquid has dried up, simply add some boiling water to the bottom of the pan.

Continue cooking the lamb for another 1.5 hours.

At 4 hours, the lamb should pull away from the bones and if you tug at the meat, it should shred.

Remove the tray/dish from the oven and set aside for about 20 minutes. Serve with a rice salad or fattoush salad, tzatziki dip and pita bread.