1. Partially freeze steak; trim fat. Slice steak diagonally across grain into very thin strips; cut strips into 2-inch pieces.
2. Coat a large nonstick skillet with cooking spray; place over medium-high heat until hot. Add steak, and cook 5 minutes or until browned on all sides. Remove steak from skillet; drain. Wipe drippings from skillet with a paper towel. Coat skillet with cooking spray. Add onion; cook, stirring constantly, 5 minutes. Add mushrooms; cook, stirring constantly, 3 minutes. Combine water, flour, paprika, and bouillon granules, stirring until smooth; add to skillet. Stir in steak. Reduce heat to medium-low; cook, stirring constantly, until mixture reaches a simmer. Cook, uncovered, an additional 10 minutes, stirring occasionally.
3. Remove skillet from heat; stir in sour cream, salt, and pepper. To serve, spoon 3/4 cup noodles onto each serving plate; spoon beef mixture evenly over noodles. Sprinkle with minced parsley, if desired.