Cut the onion, carrot and pickle in match-stick style pieces.
Lay out the thin slices of meat and each spread generously with mustard and sprinkle with salt and pepper.
Place bacon on top (if using) and then pickle, carrot and onion along the meat. Roll up tightly and secure with toothpicks.
Heat a large dutch oven or pot over medium-high heat. Add butter or oil. Add cook, turning occasionally, until browned on all sides.
Add 1 cup water or beef broth to the pot and scape up any browned bits from the pan. Cover pot and simmer on low for 2 hours.
Remove Rouladen to a plate and bring juices in the pot to a boil. Thicken with cornstarch dissolved in 1 Tablespoon of water. Taste gravy and add additional salt, pepper, or beef bouillon granules, if desired.
Remove toothpicks from the Rouladen and serve with gravy spooned on top.
