In a large heavy pot, combine half of the celery, carrots, onion and parsley and bring to a boil.
Lower heat and simmer for 1 1/2 hours.
Remove from heat and remove chicken.
Strain soup and place broth in plastic container and cool.
Remove all meat from chicken and refrigerate.
The next day remove fat from the top of broth and put back on stove.
Add the other half of the carrots, celery and onion.
Add parsnips and chicken and bring the soup to a boil.
Lower to a simmer for 1 hour.
Add the parsley at the end and serve.