Turkey Stock

Name: Turkey Stock
Ingredients: 5 pound turkey parts such as wings, drumsticks, and thighs; 2 medium yellow onions, left unpeeled, trimmed and quartered; 2 celery ribs, cut into 2-inch lengths; 2 carrots, cut into 2-inch lengths; 4 quart cold water, divided; 5 parsley stems (without leaves); 1 Turkish bay leaf or 1/2 California; 8 black peppercorns; Equipment: a 17- by 14-inch flameproof roasting pan