1. Chop onion, garlic and carrots and place into the slow cooker.
2. Heat oil in a fry pan and sear the lamb shanks. Cook for about 30 seconds on each side.
3. Remove shanks from pan and place into the slow cooker.
4. Pour the wine, stock and passata into the slow cooker along with the rosemary.
5. Season with salt and pepper.
6. Leave in cooker on low heat for at least 4 hours or until cooked.
7. In the last hour of cooking, put heat up to high.