Instructions:
1. Prepare the Salisbury Steaks:

In a large bowl, combine the ground beef, breadcrumbs, milk, chopped onion, egg, garlic powder, onion powder, Worcestershire sauce, salt, and pepper. Mix well until fully combined, but be careful not to overwork the meat.
Divide the mixture into 4 equal portions and shape each into an oval or round patty, about 1/2-inch thick.
Heat olive oil in a large skillet or frying pan over medium heat. Once hot, add the patties and cook for 4-5 minutes per side, or until they are browned and cooked through (internal temperature should be 160°F). Remove the patties from the skillet and set aside on a plate.
2. Make the Mushroom Gravy: