Place the bones in a large saucepan, cover with water, bring to a boil, and boil for 5 minutes.
Drain and rinse the bones.
Put the bones in a large, clean stockpot and add the onion, carrot, celery, and cold water.
Bring to a simmer and cook gently, skimming the surface from time to time, for 2 hours.
Strain the consomme through a very fine strainer or a strainer lined with cotton cloth and season with salt and pepper.