Place carcasses in a large pot. Add onion, carrot, celery, garlic and water. Bring to a boil, skimming foam. Reduce heat to low and add herbs, peppercorns and salt; simmer gently, uncovered, for 2 hours. Strain through a fine sieve into a large bowl. (Discard solids.) Let cool slightly, then refrigerate until cold. Skim off fat.Advertisement
Make Ahead Tip: Refrigerate for up to 2 days or freeze for up to 6 months.
Nutrition Note: Analysis note: After straining and skimming, broth has negligible calories and nutrients except sodium (120 mg per cup).