In a large, deep skillet melt the butter over medium-high heat. Add the mushrooms, onion, and garlic; cook for 6-8 minutes or until the mushrooms have released their liquid.
Add the beef and break it up with a wooden spoon and cook 8-10 minutes, or until the beef is fully cooked and browned.
Add the gravy mix and flour. Stir constantly for 2 minutes, and then stir in the broth, Worcestershire, pepper, and salt. Bring mixture to a simmer and cook, uncovered, for 10 minutes, stirring occasionally.
Remove from heat, and stir in parsley and sour cream. Serve over hot boiled egg noodles. Garnish with chopped parsley if desired.