Drizzle a shallow cast cast iron casserole with plenty of olive oil (unless you are making the Slimming World variation, see below). Add the potatoes and season with plenty of salt and pepper. Sprinkle with the oregano and then toss everything together.
Add the hot stock, lemon wedges, garlic cloves and rosemary. Cover the casserole and cook for 30 minutes. If you don’t have a casserole you can use a roasting tin and cover it with foil for the first part of the cooking.
Carefully remove the casserole from the oven. Uncover the dish and squeeze the lemon juice from the wedges (remove any pips!). Give everything a good turn. Continue to cook for a further 30-45 minutes or until the potatoes are fork tender.