Chile Rellenos de Queso

Heat the broiler. Place the chiles onto a baking sheet. Broil until the skin is blackened on all sides. Remove the chiles to a gallon size resealable plastic bag. Seal the bag. Let stand for 20 minutes. Remove the skin from the chiles. Cut a lengthwise slit in the side of each chile and remove the seeds. Rinse the peppers with cold water and pat dry with a paper towel.Stir the bread crumbs, cheeses and cumin in a medium bowl. Season with the black pepper. Spoon the cheese mixture into the chiles. Coat the chiles with the flour.Beat the egg whites in a medium bowl with an electric mixer on high speed until stiff peaks form. Add the egg yolks, one at a time, beating well after each addition. Dip the chiles into the egg mixture.Heat the oven to 350°F. Pour vegetable oil into a 12-inch deep-sided skillet to 3/4-inch deep and heat over medium-high heat. Add the chiles and cook until they're golden brown on all sides. Drain the chiles on paper towels. Place the chiles into a 2-quart shallow baking dish. Sprinkle with additional Cheddar cheese.Bake for 5 minutes or until the cheese is melted. Sprinkle with the green onion, if desired.