To make the broth:
1. In a narrow, deep pot just large enough to hold the chickens (10- to 12-quart capacity), place the chickens, onions, celery, carrots, parsnips, and parsley. (Make sure you use a narrow pot rather than a wide one. Otherwise, you may have to use too much water to cover the chickens.) Add just enough cold water to barely cover the chickens (ideally, not more than 5 quarts, or 20 cups). Bring to a boil over high heat, skimming off any scum that rises to the surface. Reduce the heat to a simmer (rapidly boiling soup or stock often makes it look cloudy instead of clear) and season with 2 teaspoons of salt and 1 teaspoon of pepper. (You’re seasoning here because you want the chicken to have some flavor when you use it later in other dishes. The soup will be seasoned again later.)
2. Simmer the broth, uncovered, for at least 3 hours. Season again with 2½ teaspoons salt and 1 teaspoon pepper. Taste; if it tastes like chicken, it’s ready. If not, let it cook a bit longer and taste again. It can cook for another hour as long as it is barely simmering, but no more than 4 hours total or the chicken will dry out.
3. When the broth is done, turn off the heat, lift the chicken from the pot with slotted spoons or a spider (see Love Note 1), and set aside in a large bowl or on a rimmed baking sheet until cool enough to handle.
4. Strain the broth into a clean 6- to 8-quart pot, and discard the solids. If you’re not making the soup right away, cool and refrigerate the broth so you can scrape off the solidified fat from the surface before continuing. Otherwise, allow the stock to sit undisturbed for at least 10 minutes, and spoon off the fat that rises to the surface.
To make the soup:
1. Set the pot of broth over medium heat and bring to a simmer.
2. Add the diced carrots and celery to the simmering broth, and cook until just fork-tender, about 8 minutes (see Love Note).
3. Taste the soup and adjust the seasoning with more salt and pepper, if necessary.
4. While the vegetables are cooking, pick the meat from the chicken, leaving the pieces as large as possible, and set aside. Discard the bones.
1. Add the 2 cups of cooked chicken to the soup.
2. Divide the cooked noodles among the serving bowls. Ladle the soup over the noodles, sprinkle with the fresh chopped dill, and serve.