Chiles Rellenos with Cheese - Rick Bayless

Ingredients

• Vegetable oil to a depth of 1 inch for frying
• 6 medium (a generous pound) fresh poblano chiles, not twisted or deeply indented, preferably with long stems
• 1 pound Mexican melting cheese (Chihuahua, quesillo, asadero or the like) or Monterey Jack, brick or mild cheddar, shredded (you’ll have about 4 cups)
• 2 tablespoons vegetable or olive oil or rich-tasting pork lard
• 1 medium onion, chopped into ¼-inch pieces
• Three 15-ounce cans good-quality tomatoes in juice (preferably fire-roasted), undrained
• 2 1/2 cups chicken broth
• Salt
• 6 eggs, yolks separated
• 2 tablespoons all-purpose flour, plus about ¾ cup for dredging
• Big sprigs of watercress or flat-leaf parsley, for garnishing the plates