1) Season lamb and sear, fat side down.
2) Place in roasting pan, rack side down, and cook at 400 degrees for 15 minutes for medium-rare.
3) Remove from oven and let rest 1 minute.
4) Coat fat side of each rack with Dijon mustard and breadcrumbs.
5) Return to oven until golden brown; let rest a few minutes before carving.
To French-cut a rack of lamb means to cut all meat and tissue off the bones, leaving just the chops connected to the cleaned bones.