Cut the roulades into thin strips as you would with strips of meat. Cut the onion and the beef into large cubes and the gherkins into slices.
Fry the meat in a little oil. When the leaked liquid has evaporated, add the onion and the beef and fry briefly. Now add the cucumber. Season with salt and pepper, deglaze with the beef stock and bring to the boil briefly. Now stir in the mustard and cover and simmer at a low temperature for approx. 45 minutes. Stir in the gravy and season to taste, if necessary thicken with a sauce thickener.