Preheat the oven to 150°C fan (170°C conventional).
Place the cinnamon, cumin, coriander and cardamom pods into a dry frying pan over a medium heat. Toast them for a minute or two until fragrant, then tip them into a pestle and mortar and crush them fairly coarsely. Pick out and discard the cardamom husks, then stir the turmeric into the ground spices along with a generous seasoning of salt and pepper.
Place the lamb into a large bowl, add 2 tablespoons of the olive oil and the spice mixture, then tumble everything together until every piece is well coated.
Heat a large casserole or heavy-based pan over a medium-high heat. Add the remaining olive oil and brown the lamb well in batches, taking your time so the meat colours rather than steams. Lift the browned lamb onto a plate as you go.
Lower the heat slightly and add the sliced red onions to the same pan. Cook for 10–12 minutes, stirring regularly, until they've softened and are beginning to colour. Add the garlic, chilli and ginger and cook for another couple of minutes.
Stir in the tomato purée, then add the prunes, saffron, preserved lemon, bay leaves and about 250ml water. Return the lamb and any resting juices to the pan, scatter over the thyme, bring everything to a gentle simmer, then cover tightly with a lid.
Transfer to the oven and cook for about 2½ hours, or until the lamb is almost completely tender. Check it from time to time and add another splash of water if it looks a little dry.
About 30 minutes before the end of the cooking time, stir in the drained chickpeas, return the pan to the oven with the lid off to finish cooking.
Once the lamb is meltingly tender, remove the casserole from the oven and leave it to rest for 10–15 minutes. Scatter over the chopped mint and trickle generously with the honey just before serving.
Bring the pot straight to the table and serve with plenty of fluffy rice.
