Prepare the marinade by pounding the garlic, ginger and chilli with the salt in a mortar with a pestle to form a coarse paste.
Add the coriander and parsley and continue to pound to a paste.
Beat in the cumin, ground coriander, olive oil, honey and lemon juice.
Cut small incisions in the shoulder of lamb with a sharp knife and rub the marinade all over the meat, making sure it goes into the incisions.
Cover and marinate in the refrigerator for at least 6 hours or overnight.
Place the shoulder of lamb in the base of a tagine and pour over the olive oil.
Scatter the onion wedges around lamb and pour over the measurement water.
Cover and place in a preheated oven, 180°C , Gas Mark 4, for about 1 hour 20 minutes.
Melt the butter in a heavy-based frying pan over a medium heat, add the quinces and stir to coat well, then sauté for 4 minutes, depending on size, until golden brown.
Remove the tagine from the oven.
Arrange the quinces around the lamb and drizzle the honey over the quinces.
Re-cover, return to the oven and cook for 15 minutes, then remove the lid and cook for a further 10 minutes.
Scatter the chopped parsley over the top of the lamb and serve with lemon wedges.
