Grated Parmesan cheese (opt) Prepare linguine according to package directions except omit salt. Drain; keep warm. Cook mushrooms & celery in hot margarine till tender. Stir in cornstarch. Stir in next 5 ingredients. Cook & still till bubbly. Stir in cheese till melted. Stir in chicken and spinach. Cover & cook 1 minute or until heated through. Serve over linguine. Sprinkle with Parmesan.