2. Heat the olive oil in a large casserole pot. Add the onion and garlic and gently sauté them until golden brown.
3. Pour the red wine into the pan and bring to fast boil. Reduce the wine by two-thirds then add the tomatoes, rosemary, bay leaves and stock. Bring the liquid to to a simmer then add the lamb shanks.
4. Cut a large round of silicone paper to fit tightly inside the pot on top of the lamb shanks. Once covered, place the casserole in the oven for two hours, checking the shanks from time to time to ensure they aren't drying out.
5. If the liquid seems to be drying up too quickly, simply top up with a little water. After two hours the meat should be tender and come away from the bone easily.
6. Transfer the lamb shanks to a serving dish using a slotted spoon, leaving the cooking stock in pot. Bring to the boil, skimming off any fat. Leave it to reduce until thickened to a light sauce.
7. Whisk the cold butter into the sauce, then add sugar and red wine vinegar. Taste and adjust the seasoning if necessary.
8. Pour the sauce over the lamb shanks and serve with a couple of branches of rosemary and root vegetables - parsnips, carrots and potatoes are perfect.
Recipe courtesy of Great British Chefs