In 10-inch nonstick skillet, melt butter over medium heat. Cook mushrooms, onions and garlic in butter 5 to 7 minutes, stirring occasionally, until tender.
Remove from skillet to small bowl; set aside.
Increase heat to medium-high. In same skillet, cook beef 5 to 7 minutes, stirring frequently, until no longer pink; drain.
Stir in 1 cup of the beef broth, the Worcestershire sauce, salt and pepper; heat to boiling.
Beat flour and remaining 1/2 cup beef broth with whisk until incorporated; stir into beef mixture.
Add mushroom mixture; return to boiling, and stir constantly about 1 minute or until mixture thickens. Remove from heat; stir in sour cream.
Serve with cooked egg noodles. Garnish with parsley.