Instruction

1. Cut steak horizontally from a long side to within 1/2 in. of opposite side. Open steak so it lies flat; cover with waxed paper. Flatten to 1/4-in. thickness.
2. In a small bowl, combine the lemon juice, soy sauce, honey, mustard, pepper and, if desired, lemon zest. Pour half of marinade into a large shallow dish; add beef and turn to coat; cover and refrigerate overnight. Cover and refrigerate remaining marinade.
3. In a large skillet, saute mushrooms and onion in butter until tender. Remove from the heat; stir in parsley. Drain steak and discard marinade. Open steak; spoon filling over steak to within 1/2 in. of edges. Roll up tightly jelly-roll style, starting with a long side. Tie with kitchen string. Place in a greased shallow roasting pan. Pour reserved marinade over steak.
4. Cover and bake at 350° for 45 minutes. Uncover; baste with pan drippings. Bake 30 minutes longer or until meat reaches desired doneness (for medium-rare, a thermometer should read 135°, medium, 140°, medium-well, 145°). Remove and keep warm. Meanwhile, transfer cooking juices to a saucepan; skim fat. Bring cooking juices to a boil. Mix cornstarch and broth until smooth. Stir into cooking juices. Bring to a boil; cook and stir 1-2 minutes or until thickened. Slice steak and serve with sauce.