Rinse the chicken well and place it in a large soup pot. Stud each onion half with a clove, and add them to the pot along with the celery, carrots, parsnips, garlic, sprigs of dill and parsley, and salt and pepper. Add the water and bring to a boil. Reduce the heat, cover, and simmer for 2 hours. Occasionally skim off any foam that forms on top.