Trim fat from beef. Partially freeze beef. Thinly slice beef across the grain into bite-size strips.
In a large skillet cook and stir the meat in margarine or butter until meat is brown. Remove meat from skillet; set aside.
Add mushrooms, onion, and garlic to skillet. Cook and stir until vegetables are tender. Stir in water, pasta, bouillon granules, and pepper. Bring to boiling; reduce heat. Cover and simmer about 12 minutes or until pasta is tender, stirring frequently.
Meanwhile, stir together sour cream or yogurt and flour. Stir sour cream mixture and parsley into the pasta mixture. Return beef strips to the skillet. Cook until bubbly, stirring gently. Cook and stir for 1 minute more. Makes 4 main-dish servings.