Season the lamb chops lightly on both sides with salt and pepper.
Reserve a dot of the butter and melt the remainder in a frying pan on the hob. Fry the chops until lightly browned, then transfer to a shallow casserole dish. Add the onion, garlic and rosemary to the frying pan and fry gently for 3 minutes. Scatter over the lamb in the casserole.
Layer the potatoes on top and pour over the stock. Dot with the reserved butter, season lightly with salt and pepper and cover with foil. Place on the lower rack of the halogen oven.
Set the temperature to 200°C (392°F) and cook for 30–40 minutes until the potatoes are tender. Remove the foil and cook for a further 10 minutes until the surface is golden. Serve the hot pot with seasonal green vegetables.