Preheat the oven to 200C/180C Fan/Gas 6. First cook the beef by placing a large saucepan over a high heat, add 1 tablespoon of the oil and brown the beef pieces. Do this in batches so the pan isn't too full. Remove the beef from the pan and set aside on a plate. Don't clean the pan, as you'll need this to fry the vegetables.
While the beef is frying, peel and chop the onions and carrots and slice the celery.
Heat the remaining oil in the same saucepan and fry the onion, celery and carrot for 4–5 minutes or until the onions have softened. Scrape any cooked on bits from the bottom of the pan. That will add flavour to the stew. Season with salt and pepper.
Mix the beef in with the vegetables, then take the pan off the heat. Tip the meat and vegetables into a large ovenproof dish and pour the stock over the top.
Peel and slice the potatoes into ½cm/¼in thick slices and arrange over the top of the beef. Dot the butter over the top then cover tightly with foil. Bake for 1 hour then remove the foil and bake for a further 15 minutes until the potatoes are crisp and golden-brown. Serve in deep bowls.