1. Preheat the oven to 200°C. Trim off any excess fat from the lamb racks. Cut small slits in the top of the lamb with a small, sharp knife. Insert slices of garlic and small pieces of rosemary into the slits. Sit the lamb on a plate.
2. Whisk together the honey, wholegrain mustard and mint sauce and brush over the lamb racks. Allow to marinate for 20 minutes in a cool place.
3. Put the lamb racks into a baking dish and spoon on any sauce that may be left behind on the plate. Bake for 20 minutes for medium rare, or until cooked to your liking, basting a couple of times during cooking with the honey mustard mixture.
4. Remove from the oven and allow to stand, covered, in a warm place for 10 minutes to allow the juices to be absorbed back into the meat. At this stage you can either cut the lamb into individual cutlets or leave the rack intact and serve as is.
A Chinese cleaver will allow you to cut the racks into cutlets effortlessly. If you do not have one of these use a large sharp knife. Avoid using serrated knives as they tend to tear the meat rather than slicing cleanly.