Heat oil in a large pan over HIGH heat. Brown shanks (You may need to do this in batches) then add to slow cooker with carrots and celery.
Combine tomato and recipe base then pour over lamb. Cover and cook for 4 hours on HIGH or 8 hours on LOW (Keep covered during cooking. Cooking times may vary between slow cooker models, we used a 5.5 L appliance).
Serve with mashed potato, topped with fresh rosemary.
NO slow cooker, NO problem place prepared lamb shanks in an ouen proof dish, cover and cook at 160°C (140°C fan-forced) for 4 hrs or until tender.