In a large bowl, combine the ground beef, egg, Worcestershire sauce, Dijon mustard, minced garlic, seasoned breadcrumbs, onion powder, salt, and pepper. Mix until just combined, being careful not to overwork the meat.

Shape the mixture into 4 oval patties.

Heat a drizzle of avocado oil in a large skillet over medium to medium-high heat. Add the patties and cook for about 4–5 minutes per side, or until browned and mostly cooked through. Remove the patties from the skillet and set aside.

Reduce the heat to medium. Add the butter to the same skillet and let it melt. Sprinkle in the flour and whisk until smooth. Cook for about 1 minute, whisking often.

Slowly pour in the beef broth while whisking to prevent lumps. Add the Worcestershire sauce and garlic powder, then continue whisking until the gravy starts to thicken.

Add the patties back into the skillet and spoon some of the gravy over the top. Let everything simmer for about 5–8 minutes, or until the patties are cooked through and the gravy is thickened to your liking.

Serve warm with plenty of gravy spooned over the top.