While the noodles are cooking, add the cornstarch and milk to a medium saucepan. Stir to combine. Slowly stir in the chicken broth. Add the poultry spice, onion powder, garlic powder, parsley, and pepper. Cook over a medium-low flame and use a whisk to stir continuously until the sauce thickens.
Place the drained noodles in the casserole dish. Add the chicken, peas, carrots, corn, onion, and celery to the pasta. Stir to combine. Pour the sauce over the noodle mixture and stir to thoroughly combine.
Place foil over the pan and bake at 350 degrees for 20 minutes.
Remove the foil and top with shredded cheese. Place it back in the oven for 10 minutes or until the cheese is melted.