Morocco is famed for its slow-cooked tagines, or stews, made in a distinctively shaped earthenware pot. This is my take on them, made in a regular casserole dish, but including all the sweet spices you’d expect. Make sure you get plenty of color onto the lamb as this is what gives the stock its wonderful depth of flavor. The dish will be even better if made a day in advance and reheated.
Heat a large, heavy-bottomed casserole dish over high heat. Add a little oil and brown the lamb pieces in batches for about 5 minutes until colored all over. Remove and set aside.
Add a little fresh oil to the pan, then add the onions and a good pinch of salt and pepper. Cook for 4–5 minutes until lightly colored, then add the garlic, ground ginger, saffron, ground coriander, cumin seeds, paprika, fennel seeds, cinnamon stick, and bay leaf. Stir for 2 minutes until aromatic.
Add the tomato purée and stir for 30 seconds, then add the sweet potato, coating well with the mixture in the pan. Return the lamb, plus any resting juices, to the pan along with the raisins and stock. Bring the stock to a boil, scraping up any bits stuck to the bottom of the casserole dish.
Lower the heat and simmer very gently, uncovered, for 1–2 hours, stirring occasionally, until the lamb is very tender. If the liquid is reducing too much, cover the casserole dish or add a cupful of water. This dish will be delicious if left overnight once cooked and gently reheated so that the flavors have even longer to develop.