MAKES ABOUT 15 CUPS

3 medium yellow onions, halved
12 lbs. beef shin bone, cut into pieces
3 stalks celery, trimmed
2 medium carrots, peeled
3 leeks, trimmed
1 bunch fresh parsley
1 Bouquet Garni

1. Put onions, cut side down, in a large stockpot over high heat and cook without turning until scorched, about 5 minutes. Transfer onions to a bowl.

2. Working in batches, add shin bone to pot and brown meat on all sides, 5–10 minutes per batch.

3. Reduce heat to medium-high, and return meat and onions to pot along with celery, carrots, leeks, parsley, and bouquet garni. Cover and cook for 20 minutes. Add 6 quarts water, bring to a boil, reduce heat to medium, and simmer, uncovered, for 2 1⁄2 hours, skimming off scum as it cooks. Strain stock, chill, then remove fat.