• Gather and measure all ingredients before starting.

Make Patties:

• In a large bowl combine the ground beef, salt, pepper, garlic powder, ketchup, Worcestershire sauce, steak sauce, egg, and breadcrumbs until evenly mixed.
• Divide the mixture into four equal portions and shape each into an oval patty.

Cook Patties:

• Heat the canola oil in a large deep skillet over medium-high heat until shimmering but not smoking. Add the patties and cook about 3 minutes per side until well browned.
• Transfer the browned patties to a plate and keep warm while you prepare the gravy.

Make Gravy:

• Carefully drain excess fat from the skillet, leaving any browned bits. Return the pan to medium-low heat and add the butter. When it melts and begins to foam, add the sliced onion and cook gently 4–5 minutes until softened and translucent.
• Stir in the sliced mushrooms and sauté another 3–4 minutes until they begin to release their juices.
• Sprinkle the flour over the onion and mushroom mixture, stir to combine, and cook 1–2 minutes to remove the raw flour taste.
• Increase heat to medium and slowly add the beef broth while scraping up any browned bits from the bottom of the skillet. Once the sauce comes to a simmer, nestle the patties back into the pan.
• Lower the heat to maintain a gentle simmer, cover, and cook about 20 minutes. Flip the patties 2–3 times during cooking. Uncover for the final 5–8 minutes to allow the gravy to thicken, adjusting heat as needed to keep a steady simmer.
• Taste the gravy and season with additional salt and pepper if necessary.

Assemble:

• Place one slice of white bread on each plate, set a hot Salisbury steak on top of each slice, and spoon a generous amount of the onion-and-mushroom gravy over the steak. Serve immediately.