1 Preheat oven to 400ºF.2 Sprinkle racks of lamb with salt and pepper.3 In large non-stick skillet over medium-high heat sear racks of lamb until browned, about 2 minutes on each side. Transfer to a roasting pan and let cool slightly.4 Using a pastry brush, rub mustard all over lamb. Press walnut mixture onto mustard to form a crust5 Roast in the center of preheated oven until medium rare, about 15 - 20 minutes. Remove from oven, tent with foil and let rest for 5 to 10 minutes. 6 Cut between the bones and serve 2 - 3 chops per person.