In large skillet, melt margarine over medium-high heat. Add chicken; cook and stir 5-6 min. or until browned.

Slowly add water, milk, pasta and seasoning mix; bring to a boil, stirring occasionally.

Reduce heat to medium. Boil uncovered, 5-6 min. or until pasta is just tender, stirring frequently. Stir in spinach, if desired.

Sauce will be thin. Let stand 3-5 min. to thicken.