Wash the chicken and remove the bag of gizzards from the inside. Place the chicken in a big soup pot, you'll need at least a 5 qt pot, and add enough water to cover the chicken. Add the whole onion, whole carrots and celery sticks to the pot. Make sure there's enough water to cover the vegetables. Bring to a boil over medium-high heat.
Once it comes to a boil, you will notice a dirty foam floating around the top of the pot, use a skimmer to skim that out. This will ensure that you get a clear soup. Keep skimming the foam until there's no more left. Reduce the heat to medium-low, cover with a lid and cook for about 1 hour, the carrots should be fork tender and the chicken cooked through, and almost falling off the bone.
Carefully remove the chicken from the soup pot and let it cool for a few minutes until it's cool enough so that you can pull the meat from it. Remove the carrots, celery and onion from the soup pot as well.
If you have too much broth in the pot you can now ladle some out to a jar or airtight container for later use and store it in the fridge.
Chop up the carrots and celery and add it back to the soup.
Shred some meat from the chicken, I used the meat from half the chicken, but feel free to use all the meat, especially if you have a lot of broth, then add the shredded chicken back to the soup pot.
Add the dry noodles to the pot, and the chicken bouillon or vegeta. Taste for seasoning and adjust with salt and pepper as needed.
Cook for another 5 to 10 minutes until noodles are cooked through. Be careful to not add too many noodles because as the soup sits they will expand and soak up a lot of the broth.
Garnish with parsley and serve.