In a medium mixing bowl, combine ground beef, breadcrumbs, egg, Worcestershire sauce, onion powder, garlic powder, salt, and pepper.
Form the beef mixture into 4 equal oval-shaped patties approximately 3/4-inch thick.
Heat vegetable oil in a large skillet over medium-high heat.
Sear the patties for 3-4 minutes per side until deeply browned; remove from skillet and set aside.
Reduce heat to medium and add butter to the skillet.
Sauté mushrooms and onions for 6-8 minutes until caramelized and tender.
Sprinkle flour over the vegetables and cook for 1 minute, stirring constantly.
Slowly whisk in beef stock, scraping the bottom of the pan to release fond.
Simmer the gravy for 3-5 minutes until thickened.
Stir in the heavy cream until fully incorporated.
Return patties to the skillet, spooning gravy over them, and simmer for 5 minutes or until internal temperature reaches 160 degrees Fahrenheit.
Serve immediately.