Put the chickpeas into a large bowl, cover with plenty of fresh cold water and soak for 12 hours or over night.
Preheat the oven to 200C. Sit the mutton shoulder in a large, deep roasting tray. Trickle over half the olive oil and season generously with plenty of salt and pepper. Place in the hot oven for 20–30 minutes so that it takes on some colour.
In a pan, put the onions in and season with a little salt and pepper then cook, stirring occasionally, until the onions are beginning to soften and everything smells amazing. Add the soaked drained chickpeas and cook them with the onions for a further 5 minutes. Add the stock and bring up to a gentle simmer.
Take the roasting tray from the oven and lift the mutton shoulder out onto a plate. Now add the soaked chickpeas to the roasting tray along with the stock, sliced onions, garlic, chilli, toasted crushed spices, lemon zest and rosemary sprigs. Season with salt and pepper, give the tin a shake to even them all out then place the mutton back in. Foil the tray over or cover with baking parchment, this which will help to seal in all the steam as the meat cooks.
Turn the oven down to 150C, set the tray in the middle of the oven and cook slowly it’ll take 4 - 5 hours. To test if the meat is cooked, lift away the foil and make sure the meat is coming away from the bone. It should be fork tender. Scatter over the freshly chopped flat leaf parsley and the lemon juice. Taste and adjust the seasoning if required.
Serve the mutton with the chickpeas, a sharply dressed tomato salad and some warm flat breads or pitta.