1. Cook noodles according to package directions; drain.
2. Heat oil in a large skillet over high heat; swirl to coat. Add beef; sprinkle with 1/4 teaspoon salt and 1/4 teaspoon pepper. Cook 4 minutes or until browned, turning to brown on all sides. Remove beef from pan.
3. Reduce heat to medium-high. Add leek, thyme, garlic, and mushrooms; sauté 5 minutes or until lightly browned, stirring occasionally. Sprinkle mushroom mixture with flour and paprika; cook 30 seconds, stirring constantly. Add stock; bring to a boil. Reduce heat, and simmer 2 minutes or until sauce is thickened, stirring frequently. Stir in beef, remaining 1/2 teaspoon salt, remaining 1/4 teaspoon pepper, and sour cream. Serve over noodles; sprinkle with parsley.