Mix ground beef with breadcrumbs in bowl.
Add egg and Worcestershire sauce to mixture.
Season with garlic powder and onion powder.
Add salt and pepper to taste.
Form mixture into 4 oval patties.
Heat oil in large skillet over medium.
Cook patties 4 minutes per side.
Remove patties and set aside temporarily.
Add butter to same skillet immediately.
Cook sliced mushrooms until golden brown.
Sprinkle flour over mushrooms and stir.
Slowly add beef broth while whisking.
Add Worcestershire sauce to gravy mixture.
Return patties to skillet with gravy.
Simmer 10 minutes until heated through.