Put the potato cubes and onions into a large roasting tin then sprinkle with the fennel seeds and seasoning. Tuck the orange rind strips in among the potatoes and drizzle with the orange juice and oil.
Make a space in the potatoes for the lamb and put in a single layer with the fat uppermost. Season the fat, cover and chill until required.
When ready to serve, remove the cover and drizzle the lamb fat with the maple syrup. Roast in a preheated oven, 200°C (400°F), Gas Mark 6, for 20–25 minutes for medium rare or 30–35 minutes for well done. Cover with foil towards the end of cooking for well done lamb.
Lift the lamb out of the tin, wrap in foil and leave to stand for 10 minutes. Stir the potatoes and continue cooking for another 10 minutes until brown around the edges. Spoon on to serving plates, cut between the bones of the lamb and serve 3–4 cutlets per portion. Serve with steamed green beans, if liked.