Pound beef slices and season with salt and pepper.
Spread mustard on each slice, then top with bacon, pickles, and onion.
Roll up tightly and secure with toothpicks or twine.
Brown rolls in butter and oil in a Dutch oven, then set aside.
Sauté onion, garlic, leek, carrot, and celery in same pot.
Add wine and simmer, then stir in broth, paste, bay leaf, sugar, and seasonings.
Return rouladen to pot, cover and cook 90 minutes.
Remove rouladen, strain gravy, and thicken with slurry.
Whisk in cold butter and optional cream, season to taste.
Return rouladen to gravy and warm before serving.
