Preheat the oven to 160°C (325°F).
Trim any excess fat from the Lamb Shoulder and cut into 2–3 cm pieces. Rinse, trim and slice the Lamb Kidney (remove any outer membrane), then pat both meats dry.
Season the lamb and kidney with Salt and Black Pepper, then toss in Plain Flour to lightly coat.
Heat a generous splash of Vegetable Oil together with about half the Butter in a large, ovenproof casserole over medium–high heat. Brown the floured meat in batches until well coloured on all sides, transferring each batch to a plate.
Reduce the heat to medium and add the sliced Onion and chopped Carrot to the pot; cook until softened and beginning to caramelise, scraping up any browned bits from the base.
Return the browned meat to the pot, sprinkle in a little extra flour if the pan is very wet, then pour in enough Stock to just cover the meat. Stir in the Worcestershire Sauce, add the Bay Leaf and a few sprigs or 1 tsp of dried Thyme, and bring to a gentle simmer. Adjust seasoning with more Salt and Black Pepper to taste.
Cover the casserole and transfer it to the preheated oven. Braise for about 1¼–1½ hours, until the meat is tender and the flavours have melded.
Meanwhile, peel and thinly slice the Floury Potato to about 3–4 mm thickness. When the meat is tender, remove the pot from the oven and carefully spoon the meat and gravy level in the dish.
Layer the potato slices over the top of the stew in overlapping circles, covering the surface. Dot the potatoes with the remaining Butter and season the top lightly with Salt and Black Pepper.
Return the pot to the oven, uncovered, and bake for a further 25–35 minutes until the potatoes are tender and nicely golden on top.
Remove from the oven and let the hotpot rest for 10 minutes before serving so the gravy settles. Spoon out generous portions of meat and potato and enjoy.
