1) In large kettle combine chicken, water, onion, salt, pepper and bay leaf. Bring to boiling; reduce heat. Simmer, covered, about 2 hours or until chicken is tender.
2) Remove chicken from broth. When cool enough to handle, remove meat from bones and discard bones. Cut into bite sized pieces. Or if you used frozen breasts like I do. Just cool and cut up into bite sized pieces and set aside.
3) Discard bay leaf and skim fat from broth. If you used the breasts there will be little if any, fat to worry about.
4) Bring broth to boiling. Stir in noodles, carrots and celery. Simmer, covered, about 8 minutes or until noodles are tender but still firm.
5) Stir in chicken and parsley and heat through.
Keep a couple cans of chicken broth, or maybe three or four. I sometimes get carried away with the noodles and get the soup too thick. You can use the chicken broth to thin the soup or to extend the amount you have if extra guests arrive without changing the flavor.
If you don't want to buy fresh parsley, dried parsley will do just fine. Just use less because it reconstitutes in the soup.
I like the dried noodles that look like homemade. They take a little longer to cook and use a little more chicken stock in the process. Or be creative and make your own noodles.