In a large bowl, combine the ground beef, breadcrumbs, egg, diced onion, minced garlic, salt, pepper, and Worcestershire sauce.
Mix until just combined, being careful not to overwork the meat.
Divide the mixture into 4 equal portions and shape them into oval patties.
Heat olive oil in a large skillet over medium heat.
Add the patties and cook for 4–5 minutes on each side, or until they are browned and cooked through (internal temperature should reach 160°F).
Remove the patties from the skillet and set aside.
In the same skillet, melt the butter over medium heat.
Add the sliced onion and cook for 2–3 minutes until softened.
Stir in the flour and cook for 1 minute to create a roux.
Slowly pour in the beef broth while stirring to avoid lumps.
Add Worcestershire sauce, salt, and pepper, and bring the mixture to a simmer.
Add Worcestershire sauce, salt, and pepper, and bring the mixture to a simmer.
Return the patties to the skillet and spoon some of the gravy over the top.
Cover and simmer for another 5–7 minutes to allow the patties to absorb the gravy flavors.
Serve the Salisbury steak patties with plenty of gravy over mashed potatoes, rice, or your favorite side.