Meanwhile, melt butter in medium saucepan on medium heat. Add chopped onions and garlic; cook 3 min., stirring frequently. Add flour; mix well. Cook 1 min. or until bubbly, stirring constantly. Gradually stir in broth. Bring to boil, stirring constantly; cook and stir 2 min. or until thickened. Add cream cheese; stir until melted and mixture is blended. Remove from heat; add 1/4 cup Parmesan, pepper and reserved pasta water.