Cook noodles according to package directions, omitting salt and fat.
While noodles cook, heat oil in a large skillet over medium-high heat. Add onion and mushrooms to pan; cook 3 minutes or until mushrooms are tender, stirring constantly. Add chicken to pan; cook 4 minutes, stirring constantly. Add spinach and wine; cook 2 minutes or until spinach wilts, stirring occasionally.
Combine milk and instant flour, stirring with a whisk. Add milk mixture to pan; cook 2 minutes or until sauce thickens. Stir in salt and pepper. Serve over noodles.