Combine the ground beef, breadcrumbs, beaten egg, finely chopped onion, garlic powder, onion powder, salt, and pepper in a large bowl. Mix gently with your hands or a fork until just combined. Shape into 4 to 6 oval patties about 1/2 to 3/4 inch thick.

Heat the butter or oil in a 12-inch skillet over medium-high heat until shimmering. Place the patties in the hot skillet, leaving about 1 inch between them. Cook for 3 to 4 minutes per side until a deep brown crust forms. Remove patties to a plate and set aside.

Reduce heat to medium and add the sliced onions to the skillet. Cook for 5 to 7 minutes, stirring occasionally, until soft and lightly caramelized.

Sprinkle flour over the cooked onions and stir constantly for about 1 minute to cook out the raw flour taste.

Slowly pour in the beef broth while whisking continuously to prevent lumps. Stir in the Worcestershire sauce and bring to a simmer, scraping up any browned bits from the bottom of the skillet. Let it cook for 2 to 3 minutes until it begins to thicken.

Return the hamburger steaks to the skillet, nestling them into the gravy. Reduce heat to low, cover, and simmer for 10 to 15 minutes until the patties reach 160°F internal temperature and the gravy has thickened to your liking. Taste and adjust seasoning with salt and pepper if needed. Garnish with fresh parsley before serving.