In a large bowl, combine bread crumbs, garlic, rosemary, 1 teaspoon salt and 1/4 teaspoon pepper. Toss in 2 tablespoons olive oil to moisten mixture. Set aside. Season the rack all over with salt and pepper. Heat 2 tablespoons olive oil in a large heavy oven proof skillet over high heat. Sear rack of lamb for 1 to 2 minutes on all sides. Set aside for a few minutes. Brush rack of lamb with the mustard. Roll in the bread crumb mixture until evenly coated.
For the lamb, place the lamb steak into a bowl, rub with the olive oil and season with salt and freshly ground black pepper. Heat a griddle pan and chargrill the steak for 5-6 minutes on each side, or until cooked to your liking. Leave to rest for five minutes.
Season meat with salt and pepper. Roast lamb, basting every 20 to 30 minutes, first with the reserved marinade, and then with juices that accumulate in the pan. The lamb will need to cook for about 20 minutes per pound (2 hours for a 6-pound leg of lamb, and 2 hours and 40 minutes for an 8-pound leg of lamb).An instant-read thermometer inserted in the thickest part of the meat, not touching the bone, should read 145Â° when the lamb is medium-rare. 5.nsert thermometer in the thickest part of the meat, not touching fat or bone. Roast in a preheated 325Â° oven for about 25 to 30 minutes per pound, or until meat thermometer registers 150Â° to 175Â°, depending on how well you like it done.