Preheat the oven to 190°C/ 375 °F. Heat a frying pan over high heat and season the racks of lamb with salt and pepper. Add the olive oil, garlic clove, sprig of thyme and the rack of lamb. Cook each side of the lamb for 2-3 minutes or until golden brown.
For medium rare, place the lamb in the oven for 10 minutes to heat through, then remove and allow to rest for 10 minutes. Cook for longer if preferred.
While the lamb is resting, bring the same frying pan with all the lamb juices back on heat, pour in the white wine and cook for 3 minutes. Add the beef stock or water and continue cooking for about 10 minutes or until the sauce has reduced enough to coat the back of a spoon.
To serve, carve the lamb rack into cutlets and drizzle over the sauce.