1. Preheat the oven to 200ºC, gas mark 6. Peel the potatoes and trim the edges to make 4 even-sized cubes, each roughly 6cm square by 4cm deep depending on their size. Place in a small ovenproof dish and add enough stock to reach the top of the potatoes without covering them. Bake for 40 minutes.
2. At the same time, line a roasting tray with baking parchment. Toss the carrots and parsnips in 1 tbsp oil, spread out on the tray, sprinkle with thyme then roast on the shelf below the potatoes for 40 minutes.
3. Add the leeks to the potatoes and cook for a further 10 minutes until all the vegetables are tender and the potatoes are golden brown on top.
4. Meanwhile combine the gravy and ale in a pan and warm thoroughly.
5. Heat the remaining oil in a frying pan and fry the steaks for 2 minutes on each side for medium. Allow the steaks to rest for 5 minutes before serving. Add the pan juices to the gravy for extra flavour.
6. Divide the steak and potatoes between 4 plates. Add the carrots and parsnips and top with the braised leeks. Serve with gravy.