1kgacorn squashpeeled and cut into (roughly) 2cm chunks
500mldry white wine
Trim the shoulder of lamb of its outside layer of fat and make incisions all over the flesh. The fat is normally dry and comes away easily with a knife. Cut the heads of garlic in half and slip the cloves from one of the halves out of their skins into a pestle and mortar, leaving the remaining 3 halves for later. Heat the spices in a dry frying pan for a minute or two to bring out their flavour and then add to the pestle and mortar with the salt. Grind to a rough paste before adding the Harissa, lemon zest, olive oil and rose syrup, if using.
Rub the lamb shoulder with the spice paste and leave to marinate for at least a few hours, preferably overnight. Four hours before you are ready to eat, preheat the oven to 190°C/375°F/gas 5. Lay the squash out on a deep baking tray with the lemon quarters and the rest of the garlic and place the lamb on top. Roast for half an hour, then turn the heat down to 130°C/250°F/gas ½, add the wine and continue to cook the lamb for another 3½ hours or until the meat is falling away from the bone and smells enticing.