Rinse chicken with cold water and pat dry with paper towels. Cut chicken into 1-inch pices. Prepare past according to package directions. Keep warm. Meanwhile, spray large skillet with nonstick cooking spray. Heat over medium-high heat. Add chicken, cook and stir until chicken is no longer pink. In small bowl, prepare sauce mix as directed on package. Add to chicken; bring to a boil, stirring constantly. Stir in mushrooms and peas; cook 5 minutes. Serve chicken, vegetables and sauce over pasta. Sprinkle with grated Parmesan cheese, if desired. Refrigerate leftovers.