Before you start, prep all the ingredients as listed. In a large bowl, combine the lean ground beef, egg, 1 tablespoon Worcestershire sauce, Dijon mustard, minced garlic, seasoned bread crumbs, onion powder, salt, and black pepper. Using your hands, mix until just combined. Shape the mixture into 4 oval patties of equal thickness (about 1/2-3/4 inch each) to ensure even cooking.

Heat the olive oil in a large skillet over medium-high heat for a few minutes. Once hot, add the shaped beef patties. Fry the patties for 5-6 minutes on each side, or until nicely browned. Remove the browned patties from the skillet and set aside on a plate, keeping any rendered fat in the skillet.

Add the chopped onion and sliced cremini mushrooms to the same skillet. Sauté over medium-high heat, stirring occasionally, until the vegetables release their moisture and become nicely browned, about 7-9 minutes. Transfer the cooked vegetables to the plate with the beef patties—I find that using the savory fond (the browned bits in the pan) gives the gravy better flavor.

Reduce the heat to medium. Add the butter to the skillet, letting it melt completely. Sprinkle in the flour and stir constantly, cooking for 1-2 minutes until the flour loses its raw taste and forms a roux. Gradually pour in the beef broth while whisking, ensuring no lumps remain and the mixture is smooth. Then, whisk in 1 teaspoon Worcestershire sauce and the garlic powder. Let the mixture simmer, stirring occasionally, until it starts to thicken slightly.

Return the sautéed onions and mushrooms (from Step 3) and the browned beef patties (from Step 2), along with any juices, to the skillet. Simmer everything together for 5-7 minutes, or until the patties are fully cooked through and the gravy has thickened to your liking. If the gravy becomes too thick, add a splash of water or extra beef broth to loosen it. Taste and adjust with additional salt and pepper if needed before serving. For a richer, deeper flavor, I like to finish with a grind of black pepper right before plating.