1. Place a large, flameproof casserole pot over a high heat, add 1 tablespoon of the oil and brown the lamb pieces in two batches. Remove and set aside on a plate. Reduce the heat to medium–high, add another tablespoon of oil and fry the onion, celery and carrot for 4–6 minutes or until the onions have softened.
2. Preheat the oven to 325°F
3. Return the meat to the pot, along with the bay leaf and stock, season with sea salt and ground black pepper and bring to the boil. Remove from the heat and push the slices of potato down into and across the top of the stew, dot with a little butter and give a final seasoning of sea salt and ground black pepper. Cover and place in the oven to cook for about 1½ hours or until the meat is tender, then remove the lid and cook for a further 10 minutes until the potatoes have coloured.
4. You can serve the stew straight away or leave it covered overnight in the fridge for the flavours to develop, then reheat. Serve in deep bowls with slices of white bread to soak up the liquid.