Mix all the ingredients except the cornflour paste in a flameproof casserole dish. Cover and cook over a low heat for 4 hours.
Increase the heat to high, and stir in the cornflour paste. Cook for 15–20 minutes until thickened.
Serve hot with potatoes (these can be cooked separately, or added to the casserole 25–30 minutes before the end of the cooking time if you like) or on a bed of noodles.