Tinga Sauce

• 2 tablespoons (30ml) lard or vegetable oil
• 6 ounces tomatillos, peeled (170g; about 2 medium)
• 6 ounces ripe plum tomatoes (170g; about 2 medium)
• 4 medium garlic cloves
• 1 small white onion, finely chopped
• 2 teaspoons dried oregano (preferably Mexican)
• 2 bay leaves
• 2 tablespoons (30ml) cider vinegar
• 2 cups (475ml) chicken stock (or water)
• 2 to 3 canned chipotle chilies in adobo sauce, plus 1 tablespoon (15ml) sauce from can
• 2 teaspoons (10ml) Asian fish sauce