Dust the lamb in flour.
Heat the oil in a large flameproof casserole dish over a medium heat and fry the lamb, in batches, until browned all over. Season each batch as you cook it, and set aside on a plate once cooked, until all the lamb is done.
Add the onions to the same dish, season again and cook, stirring every now and then, for 5 minutes until starting to soften. Pop the lamb back into the dish and add the kidneys.
Pour in the stock and add the Worcestershire sauce and sprigs of rosemary, if using. Season well and stir.
Cover the dish with a lid, bring to the boil, then turn the heat down and simmer very gently over a low heat for 2 hours until the lamb is tender. To check, pull a piece apart with two forks – it should shred easily.
Preheat the oven to 180°C (160°C fan)/350°F/gas 4.
Spread the sliced potatoes all around the edges of the dish. Dot with butter, then season and cook, uncovered, in the oven for 45 minutes.
Serve and enjoy!
Recipe credit from book: POTATO: Baked, Mashed, Roast, Fried by James Martin (Quadrille, £23) Photography: John Carey
Serves: 6
Preparation: mins
Cooking: mins
2kg diced lamb shoulder
1 tablespoon plain flour
2 tablespoons vegetable oil
3 large onions, sliced
6 lamb’s kidneys, cleaned and chopped
500ml lamb stock
1 tablespoon Worcestershire sauce
A few sprigs of rosemary (optional)
1kg potatoes, sliced
25g butter
Sea salt and freshly ground black pepper