1. In a large stockpot, place chicken, onions, celery, carrots, parsley, salt, pepper, and enough water to cover by 1 inch, about 4 quarts. Bring to a boil, reduce heat to medium-low, and simmer, partially covered, 1 hour. Add additional water if needed to keep chicken and vegetables covered.
2. Strain soup, reserving chicken and broth separately; discard vegetables and parsley. When chicken is cool enough to handle, pull meat off bones in chunks. Refrigerate broth for at least 1 hour, then spoon off and discard congealed fat.
3. At serving time, in a large pot, bring degreased chicken stock and dill to a boil. If using pasta sheets, cut into 3x1/2-inch strips. Add fresh or dried noodles and frozen vegetables to boiling broth. Boil until noodles are tender, about 2 minutes for fresh or about 7 minutes for dried. Return chicken to pot and heat through, about 2 minutes.