In a large mixing bowl, combine ground beef, breadcrumbs, chopped onion, beaten egg, and milk. Add Worcestershire sauce, garlic powder, and a pinch of salt and pepper. Mix gently with your hands until just combined.

Divide the mixture into four equal portions and shape into oval patties about ½ inch thick.

Heat a large skillet over medium heat and add vegetable oil. Add the shaped patties and cook for 4-5 minutes on each side until golden brown and cooked through.

In the same skillet, sauté sliced onion over medium heat for 2-3 minutes until softened.

Add beef broth and soy sauce to the skillet, scraping the bottom to incorporate browned bits. Simmer for about 5 minutes.

Whisk together cornstarch with water until smooth. Stir into the simmering gravy and cook for an additional 2-3 minutes until thickened.

Return the cooked patties to the skillet, spoon the gravy over them, cover, and heat for 5 minutes before serving.