1. Cut the meat from the bone and cube into chunky pieces. In a flameproof casserole dish, heat the oil and butter together. When it's hot, brown the meat a few pieces at a time - don't do too many at once as they will stew rather than sauté.
2. Remove the meat and place to one side. Turn the heat to a low level then add the onions and garlic. Gently sauté until soft. Sprinkle the flour and spices over the onions and continue to cook for a further few minutes (this will help thicken the sauce)
3.Remove from the heat and stir in the tomato purée and 300ml stock. Stir until the mixture is smooth.
4. Return the casserole dish to the heat and stir the mixture until boiling. Reduce the heat and add the lamb. Cover and cook for 50 - 60 minutes, stirring occasionally and adding the reserved stock if necessary. Season.
5. When the meat is cooked check the sauce. It should be thick and there should be sufficient to coat the meat. If the sauce is too runny, remove the meat and keep warm whilst you quickly reduce the remaining sauce at a high temperature.