In a mixing bowl, combine ground beef with breadcrumbs, Worcestershire sauce, and a pinch of salt and pepper. Mix gently and form into oval patties about ½-inch thick.

Heat a large skillet over medium heat and add a tablespoon of butter. Once melted, place the patties in the skillet, searing for about 5 minutes on each side until nicely browned.

In the same skillet, add sliced onions and mushrooms. Sauté for about 5-6 minutes until mushrooms are tender and onions are golden brown.

Sprinkle flour over the sautéed vegetables, stirring continuously. Cook for 1 minute, then gradually whisk in beef broth, cooking until gravy thickens.

Return the patties to the skillet, covering with gravy. Cover the skillet and reduce heat to low, simmering for about 10 minutes.

Serve the Salisbury Steak over creamy mashed potatoes or buttered egg noodles, garnished with freshly cracked black pepper.