Prep all ingredients prior to getting started.
Add all the beef patty ingredients (except for the olive oil) to a fairly large prep bowl. Using your hands, mix it together and then form 4 patties (oval shape and aim for the same thickness of about 1/2-3/4" or so for each patty).
Add the olive oil to a large skillet over medium-high heat. Allow the skillet to heat up for a few minutes.
Fry the beef patties for 5-6 minutes/side or until they're nicely browned. Transfer to a plate and set aside. Leave the fat in the skillet.
Add the onion and mushrooms to the skillet. Sauté, stirring occasionally, until the water has cooked out and they're nicely seared (about 7-9 min). Transfer to a plate (the same plate as the beef patties is fine).
Turn the heat down to medium. Add the butter to the skillet, and once it's melted, sprinkle in the flour. Cook, stirring often, for 1-2 minutes so the flour taste is cooked out.
Whisk in the beef broth slowly, ensuring the flour has dissolved into the sauce.
Whisk the Worcestershire sauce and garlic powder into the sauce.
Add the onions, mushrooms, and beef patties (and any juices from the plate) back into the skillet. Cook for another 5-7 minutes or so until the beef patties are fully cooked through and the sauce has thickened up a bit. If the gravy gets too thick, add a splash of water or more beef broth. Serve immediately with extra salt & pepper if needed.