Before we get started, I highly recommend to prepare the beef rouladen a day in advance and finish cooking them on the second day.
Gather all the ingredients for the filling.
5 rashers of bacon, 5 pieces sliced pickled gherkin, 1 onion, 2 tbsp Dijon mustard
Lay out the beef schnitzel and season them on one side with salt and pepper. Using a butter knife, spread on a thin layer of mustard.
5 large beef schnitzel, salt and freshly ground pepper to taste
Now put on a slice of bacon, followed by the sliced gherkins, and onion.
Roll the beef rouladen tightly, ensuring the sides are tucked in to keep the filling secure.
Take a lengthy piece of kitchen string and tie it around the beef rouladen as if you're wrapping a small parcel.
Heat up neutral oil in a large frying dish with a lid (I am using my Dutch oven), and sear the beef rouladen on all sides.
1/4 cup cooking oil
Once the meat has browned, add a quartered onion and some of the beef stock, then allow the rouladen to simmer for about 20 minutes with the lid on.
1 onion, 2 cups beef stock
After 20 minutes, turn off the heat, place the lid halfway on, and let the dish cool down overnight. If you prefer to finish cooking the dish in one day, proceed as outlined in the next step.