Preheat the oven to 400°F. In a large mixing bowl, combine ground beef, salt, pepper, garlic powder and onion powder. Mix until well combined. Shape the mixture into 4 oval-shaped patties and place them in a baking dish. (or place premade hamburger patties in dish with salt and pepper sprinkled on top)
In a skillet over medium heat, melt butter. Add sliced onions and mushrooms, cooking until softened and lightly browned. Sprinkle flour over the vegetables and stir to combine. Cook for an additional 1-2 minutes.
Gradually whisk in beef broth, soy sauce, salt, and pepper to taste. Continue stirring until the gravy thickens. Pour the mushroom and onion gravy over the hamburger patties in the baking dish.
Cover the baking dish with foil and bake for 25-30 minutes, or until the patties are cooked through to 160F. Optional - remove the foil during the last 5 minutes of baking for a golden finish.
Notes
Using Frozen Hamburger Patties
If you want to use ready made frozen hamburger patties you will just need to make the gravy portion. Separate the pieces and lay in the dish in a single layer. Season top with salt and pepper. Then continue with directions starting at step 2