Preheat the oven to 325F
brush the flank steaks with dijon mustard, place the bacon on top and then top with the onions and half the parsley. Season with salt and pepper.
Cut the steaks into 6 equal parts then roll them up. Use tooth picks to hold them together if necessary
melt 2 tbsp butter in a large pan and sear the rouladen on all sides til deep brown. Remove the rouladen from the pan and place in a large roasting pan.
Add the wine to the pan and deglaze, scraping up all the bits. Pour the pan sauce into the roasting dish over the rouladen. Add enough water to the roasting pan til the water level reaches about half the height of the rouladen. Cover the rouladen with the mushrooms, then cover the pan and roast at 325F for about 90 minutes.
When the rouladen is done, remove it from the pan and pour the juices through a colander into a bowl to separate the mushrooms from the juice, collecting the juices in the bowl.
Melt the butter in the frying pan, then whisk in the flour to build a roux. Whisk in the juices and worchestershire sauce. Bring the heat up to high til the gravy is on a rolling boil, then reduce to medium and simmer til thickened. Adjust flavour as needed with salt, pepper and Worcestershire sauce,