In a large bowl, combine ground beef, breadcrumbs, Parmesan cheese, parsley, egg, garlic powder, onion powder, salt, pepper, and Worcestershire sauce. Mix until well combined.

Form the mixture into 8 equal-sized patties (rissoles).

Heat olive oil in a large skillet over medium heat. Cook the rissoles for about 5-6 minutes on each side, or until browned and cooked through. Remove from the skillet and set aside.

In the same skillet, melt butter over medium heat. Add sliced mushrooms and sauté until they are browned and tender, about 5 minutes.

Sprinkle flour over the mushrooms and stir to combine. Gradually add beef broth while stirring to avoid lumps. Add soy sauce and thyme, and bring to a simmer. Cook for about 5 minutes until the gravy thickens. Season with salt and pepper to taste.

Return the rissoles to the skillet, spoon the mushroom gravy over them, and let simmer for an additional 2-3 minutes to heat through.

Serve hot, garnished with additional parsley if desired.