Crumble the ground beef into a large bowl and add the breadcrumbs, eggs, Worcestershire sauce, garlic powder, onion powder, black pepper, and salt. Mix well to combine.
Separate the hamburger mixture into 6 equal balls, and press them into oval hamburger patties.
Place the hamburger steaks in a large skillet set over medium-high heat on the stovetop. Cook until a brown crust forms, then flip and sear the remaining side. Remove the patties from the skillet and set aside.
Add sliced onion to the rendered beef drippings and saute until tender.
Reduce the stovetop to low heat, and melt butter in the skillet, then sprinkle in the flour while whisking. Continue to whisk for two minutes to prevent the flour from scorching.
Slow add the beef broth and brandy, a couple of splashes at a time, while whisking. Repeat until all of the liquid has been added.
Add the thyme sprig and fresh ground black pepper. Return the hamburger patties to the skillet and simmer them in the gravy until the patties are cooked through and the gravy has thickened.
Taste the gravy for salt, add more as needed, then serve.