Salisbury steak patties browned in a skillet, then simmered in a rich onion-mushroom gravy. A ground beef dinner ready in about 45 minutes, no oven required.
Mix and shape the patties: In a large bowl, combine the ground beef, breadcrumbs, egg, milk, 1 tsp Worcestershire sauce, onion powder, garlic powder, salt, and pepper. Mix gently and shape into 6 oval patties.
Brown the patties: Heat the oil in a large skillet over medium-high heat. Brown the patties 3-4 minutes per side, then remove them to a plate (they won't be fully cooked through yet).
Cook the onion and mushrooms: Reduce the heat to medium and melt the butter in the same skillet. Add the onion and mushrooms and cook, stirring occasionally, until softened and browned, about 6-8 minutes.
Build the gravy: Sprinkle the flour over the onion mixture and stir to coat. Cook 1 minute, then gradually whisk in the beef broth, remaining 1 tsp Worcestershire sauce, ketchup, and Dijon. Simmer until thickened, 3-4 minutes.
Simmer the patties in the gravy: Return the patties to the skillet and spoon the gravy over the top. Cover and simmer 12-15 minutes, until the patties reach 160°F.
Serve: Spoon the patties and gravy over mashed potatoes.
Notes
Brown the patties first to build a crust, then finish cooking them in the gravy so they reach 160°F without drying out.