Pat Lamb Shanks dry. Sprinkle some pepper on the lamb shanks.
Heat 2 tablespoon olive oil in a large pan, on high heat and brown the lamb shanks on all sides. Remove lamb and set aside
Wipe down the pan and add the remaining one tablespoon oil. Add the onion, bay leaf, thyme and rosemary and cook, on low heat until the onion is translucent
Add the garlic and fry for a minute
Add the celery and carrots and cook for about 5 minutes. Add the tomato paste, worcestershire sauce, lamb stock/broth and the water. Add some sugar if too acidic. Turn up the heat and bring to a boil. Add the lamb shanks back to the pot
Cover the pot with some foil and cook in the oven at 180 degrees Celsius, for 2 hours. Remove the foil and cook for a further 1 hour and 30 minutes or until the lamb is tender and falling off the bone. Reduce the cooking time or cook for longer if required
Once cooked, remove from oven. Place the cooked lamb shanks on a plate and cover with foil. Strain the contents of the pot into a bowl
Using the same pot heat melt 1 tablespoon butter. Add the cornflour and cook for a minute
Add the strained sauce and simmer on low heat until it thickens. If too thick you can add more stock. You can add more salt and pepper if required
Place the lamb shanks into the gravy. Serve hot on a bed of mashed potatoes, cauliflower mash or polenta