Cover meat with cling film and pound beef slices with the flat side of a meat tenderizer.
Spread mustard over the beef slices and top with bacon, sliced onion, and pickles. Fold sides (if possible) and shape the stuffed slice of beef into a roll. Take rolls and secure with a toothpicks (or butcher's twine).
Brown rouladen on each side over medium-high heat in a large skillet with vegetable oil (or clarified butter). Once browned remove rouladen from the skillet and set aside.
Add chopped onion, celery, and carrots to the pan and sauté over medium-high heat for 2-3 minutes. Stir in tomato pasteand add wine, beef broth, pickle juice, and bay leaf. Bring to a quick boil. If you have any leftover pickle slices add them to the mix.
Reduce the heat to a simmer and returned browned rouladen to the skillet. Braise over low heat for 90 minutes.
Remove rouladen and pour the sauce through a sieve to remove the vegetables.
Making The Gravy
Return the sauce to the pan and thicken with cornstarch. Season with salt and pepper. Add braised rouladen back into the skillet. Serve and enjoy.