Cook noodles according to package directions. Meanwhile, in a large saucepan, cook the beef, mushrooms and onion over medium heat until meat is no longer pink. Add garlic; cook 1 minute longer. Drain. Remove and keep warm., In the same pan, melt butter. Stir in flour until smooth; gradually add broth and tomato paste. Bring to a boil; cook and stir until thickened, about 2 minutes. , Carefully return beef mixture to the pan. Add the sour cream, salt and pepper; cook and stir until heated through (do not boil). Drain noodles; serve with beef mixture. If desired, top with chopped parsley.