Add the breadcrumbs to a small bowl, add the milk and stir together while adding more milk 1 tablespoon at a time to moisten the breadcrumbs fully. Let rest while you prep the rest of the ingredients (or at least 5 minutes).
Add the ground beef, bread crumb mixture, salt, pepper, chopped shallot, egg, Worcestershire sauce, soy sauce, and parsley to a large mixing bowl and mix until evenly combined.
Shape the beef mixture into 4 oval shaped patties, about an inch thick.
Heat the oil over medium high heat in a large skillet. Pan fry patties until crisp and browned on both sides (but not fully cooked). Remove from the pan and set aside.
For the gravy:
Using the same pan, add more oil if needed. Add the onion and saute until translucent.
Add the sliced mushrooms and saute until cooked through, any liquid has evaporated and mushrooms are browned (about 7 to 9 minutes). Season with salt and pepper and mix to combine.
Stir in flour and cook another minute.
Slowly add the beef stock while continuously stirring and scrape the bottom of the pan to get all the brown bits that may have stuck to the pan. Add the vinegar, raise the heat, bring to a boil, mix in the herbs, and return the beef patties to the pan.
Reduce the heat to low, cover, and simmer until patties are no longer pink in the center, about 10 minutes more.
Taste for seasoning, season with salt as needed before serving.
Notes
Be sure to mince your shallots instead of chopping them. The finer cut will allow them to cook along with the meat.
Preheat your pan well. This is important as a higher temperature is necessary to achieve a deep-colored sear on the surface of the patties.
Brown the patties until crisp, but don’t cook them all the way through. You want them to finish cooking in the sauce to allow their meaty flavor to seep into the gravy.