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 oven cooking, place the lamb in an uncovered roasting pan and cook at 165 degrees C (325 degrees F). For every 0.5 cm (inch) of thickness, allow 10 to 15 minutes of cooking time. You can allow more time for a well-done steak, cooking to an internal temperature of 76 degrees C (170 degrees F).
Quick pan sear first then roast in oven 350 degrees for 12-15 minutes if you want medium rare. This dish has a classic simplicity, and its preparation is similarly streamlined. Just brown lemon-and-thyme-seasoned lamb chops quickly, then serve drizzled with a lemony reduction of its own cooking juices. If you enjoy wine with such a main dish, try a fruity young Beaujolais, lightly chilled. Preparation time: 5 minutes. Chilling time: 1/2 to 1 hour. Cooking time: 8 to 10 minutes.