In large bowl, mix together: beef, bread crumbs, chopped onion, egg, salt, and pepper
Shape into four 3/4 inch patties
In a large skillet, over medium heat, brown patties on both sides. Approximately 10 minutes
Add broth, sliced onion, and mushrooms. Bring to a boil
Reduce heath, cover and simmer until patties are cooked (165°)
Move patties to separate dish to keep warm
Bring broth mixture back to a boil.
Mix cold water, and cornstarch in a small bowl. Stir into broth
Cook until it has become a thick gravy
Pour over patties to serve
