In a pot, place the chicken, leek greens, celery, bay leaf, Parmesan rind (if using) and water. Season with salt and pepper. Simmer over medium-low heat for about 40 minutes or until the chicken falls easily from the bones. Add water as needed so that the meat is always covered. Remove the chicken. Remove and discard the bones and skin. Shred the meat. Strain the broth. Set aside.