Step 1: Prepare the Beef Patties
In a large bowl, combine the ground beef, egg, breadcrumbs, Worcestershire sauce, garlic powder, onion powder, salt, and pepper. Mix gently and form into oval patties.
Step 2: Brown the Patties
Heat olive oil in a large skillet over medium-high heat. Cook the patties for about 4–5 minutes per side until nicely browned. Remove from the skillet and set aside.
Step 3: Cook the Mushrooms and Onions
In the same skillet, melt the butter. Add sliced onions and mushrooms. Cook for 6–8 minutes until softened and golden brown.
Step 4: Make the Gravy
Sprinkle flour over the mushrooms and onions. Stir for 1 minute. Slowly whisk in the beef broth until smooth. Add Worcestershire sauce, salt, and pepper. Simmer until thickened.
Step 5: Finish the Salisbury Steak
Return the patties to the skillet. Spoon gravy over the top, cover, and simmer for 15 minutes until fully cooked and tender.