Cook noodles to desired doneness as directed on package. Drain; cover to keep warm.
Meanwhile, heat oil in large skillet over medium-high heat until hot. If desired, sprinkle beef strips with salt and pepper. Add half of beef to skillet; cook and stir 3 to 4 minutes or until browned. Remove beef; set aside. Repeat with remaining beef strips.
Add mushrooms, onion and garlic to skillet; cook and stir over medium heat for 2 to 3 minutes or until vegetables are tender. Return beef to skillet. Add paprika; mix well. Cook 1 minute. Stir in tomato sauce.
In small bowl, combine sour cream and flour. Add to beef mixture; cook 1 minute or until thoroughly heated. If mixture becomes too thick, stir in 1 to 2 tablespoons water.
Add parsley to noodles; toss well. Serve beef mixture over noodles.