Place a casserole dish or heavy based pot onto a high heat.
Pat the meat dry using a clean cloth and then season with salt and pepper. Coat the meat with flour and use your hands to shake off any excess.
Add the oil to the pan followed by the meat. Continue to cook over a high heat until golden brown. Then remove from the heat and place into a bowl along with any juices from the pan.
Keep the pan to one side.
Preheat oven to 160'C.
Peel the onion, garlic, carrot, and potatoes. Finely chop the onions and garlic. Then slice the leeks into thick rings and cut the carrot into a rough 1cm dice. Cut the potatoes to twice the size as the carrots and celeriac. Remove the leaves from the rosemary sprigs and roughly chop.
Then in the pan used to cook the beef, add the sunflower oil with the leeks and carrot and cook over a medium heat for 3 minutes. Add the onion, garlic and rosemary to the pan and continue to cook for a further 3 minutes.
Pour in the lamb stock and bring to the boil. Once boiling, add the lamb and its juices back to the pan along with the potatoes and cover with a lid. Then cook in the oven for 2 hours or until the meat is tender.
Remove from the oven and allow to rest for 30 minutes with the lid on. Check the seasoning and add more salt and pepper if needed.
To serve, spoon the stew into a bowl and serve with crusty bread.
«You can make this stew a couple of days in advance. Keep it refrigerated in the casserole dish and reheat when ready you are ready to eat it. Ensure that it is piping hot.»