Stack beef steaks; cut lenthwise in half and thein crosswise into 3 cm wide strips. Combine marinade ingredients; add beef, tossing to coat. Cover and marinate in refrigerator 10 minutes. Meanwhile cook pasta according to package directions. Keep warm.
Remove beef from marinade; reserve marinade. Heat large nonstick wok or skillet over medium-high heat until hot. Add beef (half at a time) and stir fry 1 to 2 minutes or until outside is no longer pink. (Do not overcook). Remove beef. Keep warm.
In same skillet, combine pasta, spinach, water chestnuts, green onions and reserved marinade; cook until spinach is wilted and mixture is heated through, stirring occasionally. Return beef to skillet; mix lightly. Garnish with chili peppers. 5 servings.