Cook the Book: Onion Confit

Name: Cook the Book: Onion Confit
Ingredients: 2 tablespoons extra-virgin olive oil; 6 onions, peeled and thinly sliced (about 12 cups); Kosher salt and freshly ground black pepper; 1 cup White Chicken Stock (recipe below); 2 tablespoons white wine vinegar; 2 tablespoons fresh thyme leaves; 4 anchovy fillets, chopped (optional); 4 pounds chicken bones or 4 pounds chicken legs, wings, and backs; 1 onion, peeled and quartered; 1 carrot, peeled and coarsely chopped; 2 stalks celery, coarsely chopped; 2 leeks, white parts only, trimmed and chopped; 1 bay leaf; Peppercorns; 3 to 4 sprigs fresh flat-leaf parsley; 3 to 4 sprigs fresh thyme