Cook pasta according to package directions. Meanwhile, in a Dutch oven over medium heat, cook and stir chicken and onion in oil for 5 minutes or until chicken is no longer pink. , Stir in soup and cream. Bring to a boil over medium heat. Reduce heat; simmer, uncovered, for 2 minutes. Stir in the spinach, cheese and pepper; cook for 1-2 minutes or until spinach is wilted and cheese is melted. , Drain pasta; add to chicken mixture and toss to coat. If desired, sprinkle with parmesan and red pepper flakes.