Basic Vegetable Stock

1 onion, coarsely chopped
2 carrots, coarsely chopped
3 celery ribs, coarsely chopped
1 leek, coarsely chopped
6 fresh oregano sprigs, or 1 teaspoon dried
6 fresh thyme sprigs, or 1 teaspoon dried
1 bay leaf
1/2 tablespoon whole peppercorns

Combine all of the ingredients in a pot; cover with 12 cups of water. Bring to a boil over moderately high heat, then simmer over moderately low heat for 1 hour. Strain the stock.

MAKE AHEAD The stock can be refrigerated for up to 1 week or frozen for up to 1 month.