Preheat oven to 180℃. Heat a frying pan, add oil & fry lamb in batches to brown & seal meat. Transfer lamb to a baking pan or tagine 3.. See note 3. about alternative cooking method.
Lower the heat & sweat the onions until softened. Add harissa, garlic cloves & spices & fry briefly.
Add stock & bring to the boil. Pour over lamb, cover, and bake for 1 hour. Remove covering & bake for a further 20 minutes. Check flavour or sauce, adding a little salt if necessary. Stir through thinly sliced preserved lemon peel and serve on rice.