Preheat oven to 400°.
Place lamb on rack of a broiler pan coated with cooking spray.
Combine mustard and next 6 ingredients. Brush mustard mixture evenly over lamb. Insert a meat thermometer into thickest part of lamb. Bake at 400° for 1 hour and 22 minutes or until thermometer registers 145° (medium-rare). Let stand 10 minutes before slicing. Serve with mint jelly.