Place the lamb in a large, non-metallic bowl. Mix together the yogurt, cream, garlic, ginger, chilli powder, ground coriander and turmeric. Season well and pour this mixture over the lamb. Toss to mix well, cover and marinate in the refrigerator for 24 hours.
Allow the lamb to come to room temperature before cooking. Heat the oil in a heavy-based casserole dish, then add the fennel seeds and onions. Stir-fry for 3–4 minutes and then turn the heat to high.
Add the lamb mixture and stir-fry for 3–4 minutes. Stir in the tomatoes, bay leaf and stock, bring to the boil and remove from the heat. Stir well to combine, cover tightly and cook in a preheated oven at 150°C (300°F), Gas Mark 2, stirring occasionally, for 2 hours or until the lamb is tender. Stir vigorously to mix well and serve immediately with naan, garnished with fresh coriander.