How to Make It
Heat the oil in a large pot or Dutch oven over medium heat. Add the carrots and/or parsnips, celery, onion, thyme, 1½ teaspoons salt, and ¼ teaspoon pepper. Cook, stirring frequently, until the vegetables are tender and just beginning to brown, 10 to 12 minutes.
Add the chicken, broth, and 4 cups water. Bring to a boil, reduce heat, and simmer until the chicken is cooked through, 15 to 20 minutes. Remove the chicken and place on a cutting board. When it is cool enough to handle, shred the meat with 2 forks; discard the bones.
Meanwhile, add the pasta to the soup and simmer until al dente, 6 to 10 minutes. Add the chicken, lemon juice, and parsley and stir to combine.
This soup can be frozen in freezer-safe containers for up to 3 months. To reheat, run the containers under warm water until the soup slides out. Transfer to a pot and cook over medium heat, covered, stirring occasionally, until heated through.