Fill a pot with lightly-salted water and bring to a boil. Cook the chicken breast in the boiling water until no longer pink in the centre and the juices run clear, about 10 minutes. Cut the breast into cubes and spread in a single layer on a plate; place chicken in refrigerator for 1 hour, or until completely cooled.
Fill a pot with lightly-salted water and bring to a boil. Stir the pasta into the boiling water; cook until the pasta has cooked through, but is still firm to the bite, about 8 minutes. Drain, and rinse thoroughly with cold water to cool.
Stir the celery, Parmesan cheese, spring onions, mayonnaise, sour cream, milk, parsley, basil and thyme together in a large bowl. Fold the chicken, rotini and peas into the mayonnaise mixture. Season with salt and pepper. Chill in refrigerator for 1 hour.