Stack beef steaks; cut lengthwise in half and then crosswise into 1-inch wide strips.
Combine marinade ingredients, pour half over beef.
Cover and marinate in refrigerator 10 minutes.
Reserve remaining marinade. Meanwhile cook pasta according to package directions; keep warm.
Remove beef from marinade; discord 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 surface is no longer pink.
(Do not overcook.) Remove from skillet with slotted spoon; 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.