Classic Salisbury Steak with Savory Mushroom Gravy

Method

1. In a large bowl, combine the panko breadcrumbs with the milk and let soak for a couple of minutes. Add the beef, half the diced onion, the egg yolk, 2 teaspoons of salt, a generous grind of black pepper, the mustard powder, onion granules, and garlic granules. Mix everything together well with your hands until evenly combined, then shape the mixture into four patties about 2.5 cm thick. Set them aside.
2. Melt half the butter in a large frying pan over medium-high heat. Brown the patties for 1–2 minutes per side, then transfer them to a plate. Reduce the heat to medium, add the remaining butter to the same pan, and cook the remaining onion with 1 teaspoon of salt and some black pepper for about 5 minutes, scraping up any browned bits from the bottom of the pan.
3. Add the halved mushrooms to the pan and cook until they are nicely browned. Sprinkle in the flour and stir for 2 minutes. Stir in the tomato purée (or ketchup) and cook for another minute. Gradually pour in the chicken stock, stirring constantly, until the gravy thickens. Add the Worcestershire sauce, soy sauce, and apple cider vinegar, and stir to combine.
4. Return the patties to the pan, nestling them into the gravy. Cook over medium heat for 5 minutes, turning once, until heated through. Sprinkle with the chopped parsley and serve at once with mashed potatoes, rice, or your favorite green vegetable.