Lay flat each piece of top round, spread on a layer of mustard, sprinkle lightly with salt and pepper and top with a slice of bacon. At one end of each piece, place about a tablespoon of the chopped onions and a pickle spear. Starting from the filling side (the onions and pickle), begin to roll each piece while tucking in the sides (this will keep your rouladen filling inside as you cook them). Tie a piece of butcher string around each rouladen in the middle and then on both sides (like you would a present), and then knot it.
Heat the olive oil in a large pan on medium-high heat. Cook the rouladen on all sides until brown. Remove any excess oil from the pan, leaving the leftover brown bits. Reduce the heat, add the beef stock and bring to a simmer. Simmer on medium-low to low heat, covered, until the rouladen are fork-tender, about 90 minutes. Remove them from the pan (leaving the juices), cover loosely with foil and let rest for 10 minutes.
Whisk together the cornstarch and 1/4 cup cold water until smooth. Bring the leftover pan juices to a simmer and slowly add the cornstarch mixture while stirring. Bring to a boil, reduce the heat and simmer until the starchy flavor has been cooked away, about 10 minutes. Add the red wine near the end of the cooking time if using, to add a nice zesty flavor.
Serve the rouladen with the gravy.
This recipe was provided by a chef, restaurant or culinary professional. It has not been tested for home use.