Heat the oven to 190c/375 F/gas 5. Take a flameproof casserole with plenty of room to hold the two shoulders laid flat, place over high heat and add a generous amount of olive oil. Brown the lamb well on both sides.
Lower the heat to moderate and add the peeled button onions and a little sea salt; shake the pan from time to time so that the onions start to get a good colour. After about 5 minutes add the garlic, cumin seeds, chilli and tomatoes, stir well and increase the heat to high. Pour in the Madeira and the saffron, and when they come to the boil add the orange juice and chicken stock. Bring back to the boil, then partially cover the pan and place in the oven for 1 hour. Stir and turn the meat occasionally.
Leave to cool completely, then remove the lamb and place in the refrigerator for 1 hour.
Using a heavy knife or cleaver, cut the shoulders into three at the joints.
To serve: Reheat the meat in a non-stick pan with a little olive oil until caramelized. Remove the chilli from the sauce, then reheat the sauce until piping hot. Pour the sauce over the meat and serve with couscous.
Place the bones and calf’s foot in a large saucepan, cover with the water and bring to the boil. Skim off the scum and fat that come to the surface. Turn the heat down, add the remaining ingredients and simmer for 1 ½ hours, skimming occasionally. Pass through a fine sieve and leave to cool. This can be kept in the refrigerator for up to 5 days, or frozen.