Combine beef, breadcrumbs, egg, onion, garlic, salt, pepper, and Worcestershire sauce.
Shape mixture into 4 patties of desired thickness.
Cook patties in a skillet with a little oil for 10 minutes, or until brown on both sides.
Add beef stock, onion slices, mushrooms, and garlic to the skillet.
Bring to a boil, then reduce heat, cover, and simmer for 10 minutes.
Remove patties from skillet and keep warm.
Bring the onion mixture to a boil.
Combine water and cornstarch.
Add water and cornstarch mixture to the onion mixture.
Bring to a boil while stirring constantly for 1 minute.
Return patties to the skillet to warm up, cover with sauce, then transfer to a platter and serve.
