Cheese Stuffed Poblanos with Tomato Sauce Chiles Rellenos de Queso

Name: Cheese-Stuffed Poblanos with Tomato Sauce (Chiles Rellenos de Queso)
Ingredients: 4 large fresh poblano chiles (1 pound); 1/2 pound Monterey Jack cheese, coarsely grated (2 1/2 cups); 1 1/2 pounds tomatoes, coarsely chopped; 1 cup water; 1/4 cup chopped white onion; 2 large garlic cloves; 1 tablespoon distilled white vinegar; 1 teaspoon sugar; 1 teaspoon dried oregano (preferably Mexican); 2 tablespoons corn oil or other vegetable oil; 2 to 3 cups corn oil or other vegetable oil; 4 large eggs, separated; 1/4 cup all-purpose flour; Accompaniment: white rice; a deep-fat thermometer