To use the giblets: Empty the bag of giblets into a small pot and cover them with water plus 2 inches. Bring the water to a boil, then reduce heat and simmer for about 45 minutes to 1 hour, until everything is fully cooked. The liver will look slightly crumbly, the gizzards and heart will have a soft but firm texture. Once done, remove the giblets and finely chop them. Add the giblets to the stuffing with onions and celery, and replace half of the chicken broth with the giblet water.