Combine the cooked chicken with the Cajun seasoning, bell peppers, onion, garlic, chicken broth, tomatoes, heavy cream, cream cheese, parsley, salt, and pepper in a large freezer bag. Squish together.
Remove excess air, seal, and freeze.
Thaw.
Pour the contents of the bag into a large skillet. Bring the liquid to a boil, then add the uncooked penne pasta. Continue cooking, stirring frequently, until the pasta is tender, which should take around 15 minutes.
Top with parmesan cheese and red pepper flakes before serving if desired.