In a large bowl, add ground beef, onions, salt, ground pepper, garlic powder and onion powder. Using your hands, smash and blend everything together until the ingredients are incorporated.

Heat up a frying pan with 2-3 tablespoons of vegetable oil. Take about a tablespoon of the ground beef mixture and roll it into a 1 to 1 and 1/2 inch ball. Flatten the ball to form a patty and repeat with the rest of the ground beef. Pan fry the patties over medium heat until cooked and nicely brown. Do not overcook the patties. Set them aside on a serving plate. Reserve beef grease in the pan.

To make the mushroom gravy, heat up and melt butter in a saucepan. Once the butter starts to bubble up, add the onions and cook until soft. Add the flour and using a whisk, stir up the butter, the flour and onions together. Mixture will be thick at this point. Immediately but gently spoon about 4-5 spoonfuls of the grease from the frying pan where you cooked the beef patties. This will nicely thin the mixture slightly. Keep whisking the mixture, letting it bubble in the pan for about 4-6 minutes. Do not walk away as this roux can burn very fast.

While whisking continuously, slowly add the beef broth to the roux. The mixture will be thin and liquidy at this point. Just keep whisking until the liquid turns to a thick, silky sauce. Depending on the saltiness of your beef broth you may want to add little milk but not too much or you will thin down the gravy. If it is less salty than what you would prefer, add salt. Keep stirring the mixture with the whisk. Add the mushrooms and cook for about 2 minutes. Season gravy with ground pepper. Pour gravy over the burger patties and serve hot.