In a large mixing bowl, combine the ground beef, breadcrumbs, finely chopped onion, egg, Worcestershire sauce, garlic powder, onion powder, salt, and pepper.

Gently mix everything together using your hands or a spoon. Be careful not to overwork the meat to ensure the patties stay tender.

Once combined, divide the mixture into 4 equal portions and shape them into oval-shaped patties.

Heat a large cast-iron skillet or non-stick pan over medium-high heat.

Add a tablespoon of oil to the pan. Once hot, carefully place the patties into the skillet and cook for 4-5 minutes per side, or until browned and cooked through (internal temperature should reach 160°F).

Once the patties are fully cooked, remove them from the skillet and set them aside on a plate. Leave any drippings in the pan for the gravy.

In the same skillet, melt the butter over medium heat. Add the sliced mushrooms and chopped onions.

Cook the mushrooms and onions, stirring occasionally, until they soften and become golden brown, about 5-7 minutes.

Sprinkle the flour over the mushroom and onion mixture and stir to combine. Let it cook for 1-2 minutes to eliminate the raw flour taste.

Slowly add the beef broth while stirring, ensuring no lumps form. Bring the gravy to a simmer, and cook for another 5 minutes or until the gravy thickens to your desired consistency.

Stir in Worcestershire sauce, and season with salt and pepper to taste.

Return the cooked patties to the skillet, gently nestling them into the mushroom gravy.

Cover and let them simmer in the gravy for an additional 5-7 minutes, allowing the flavors to meld together and the patties to absorb the delicious gravy.

Serve the Salisbury steak with the mushroom gravy poured over the top.

Pair with mashed potatoes, roasted vegetables, or steamed rice for a complete meal.

Garnish with fresh parsley, if desired.