1. Trim rack of lamb, leaving the rib bones as long as possible. Leave about 5 mm / 1/4 in of fat on the outside of the rack.
2. In a small bowl, combine breadcrumbs, parsley, rosemary, garlic, mustard and olive oil. Set aside.
3. Place racks of lamb in a baking dish and cook for 15 minutes in a moderate oven. Remove from oven.
4. Press the breadcrumbs mixture on top of the rack to form a crust. Return to the oven for another 10-15 minutes.