Cook ground beef, onion, mushrooms, garlic powder, and mustard powder in a large skillet over medium heat until beef is browned and crumbly, 6 to 8 minutes.

Sprinkle flour evenly over beef mixture and stir well until coated. Stir in beef broth, Worcestershire sauce, and black pepper, scraping up browned bits with a wooden spoon. Bring to a simmer and cook until slightly thickened, 10 to 15 minutes.

Meanwhile, cook egg noodles in a large pot of boiling salted water until tender, about 7 to 9 minutes; drain.

Remove beef stroganoff from heat; stir in sour cream until blended and heated through. Serve over hot egg noodles and garnish with freshly chopped parsley.