Butterfly the flank steak by cutting lengthwise and opening like a book. Pound the steak with a mallet to a thickness of 1/4". Cut into pieces 3" wide by 8" long.
Salt and pepper both sides of the flank steak. Liberally apply mustard to one side of each steak.
In a deep skillet, saute diced bacon and onions together until bacon is cooked and onions are translucent. Add chopped Bolder Beans and set mixture aside in a separate bowl. Leave the bacon fat in the skillet.
Place bacon filling onto each steak and form into a roll. Secure roll with butchers string.
Roll each meat roll lightly in flour, and return to hot skillet with bacon fat. Turn rolls to brown all sides. When rolls are browned, add beef broth to skillet to cover rolls. Add any remaining bacon filling ingredients to broth and 2 bay leaves.
Cover skillet, and simmer on low for 1 hour. Add beef broth if level drops.
After 1 hour, remove rolls from liquid. Slowly whisk flour into beef broth until it thickens to the gravy texture you like. Make sure to scrape all of the brown bits stuck to the bottom of the skillet into the gravy.
Remove butcher string from rolls. Place meat rolls over egg noodles and smother in gravy.