Lightly salt and pepper flank steak. Spread one side with mustard. To prepare stuffing, heat vegetable oil in a frypan, add onion and cook for 3 minutes, until lightly browned. Add mushroom pieces; cook for 5 minutes. Stir in parsley, chives, tomato paste, and bread crumbs. Season with salt and pepper and paprika. Spread stuffing on mustard side of the flank steak, roll up jelly-roll fashion and tie with thread or string. To prepare gravy, cook bacon in a Dutch oven until partially done. Add the meat roll and brown on all sides, approximately 10 minutes. Add onions and saute for 5 minutes. Pour in the beef broth, cover Dutch oven, and simmer for 1 hour. Remove meat to a preheated platter. Season pan juices with mustard. Salt and pepper to taste; stir in catsup. Serve the gravy separately.