PreparationRoast chiles: Roast chiles on their sides on racks of gas burners (1 or 2 per burner) over medium-high heat, turning with tongs, until skins are blistered and slightly charred, 4 to 6 minutes. (Or broil on rack of a broiler pan about 2 inches from heat.) Immediately transfer to a large bowl and cover, then let stand 20 minutes. Make tomato sauce while chiles stand: Purée all sauce ingredients except oil with 11/4 teaspoons salt in a blender until smooth, then strain through a medium-mesh sieve into a bowl, pressing on solids, then discarding them. Heat oil in a deep 12-inch heavy skillet or heatproof casserole (preferably one that can go to the table) over medium-high heat until it shimmers. Carefully pour in sauce and simmer gently, stirring occasionally, 10 minutes (sauce should still be thin). Season with salt. Stuff and fry chiles: Carefully rub off skins from chiles, leaving stems attached. Cut a slit lengthwise in each chile with kitchen shears, then carefully cut out seedpod (including attached ribs) without tearing chile (hotter chiles smell stronger when cut). Wipe chiles clean with a paper towel if necessary. Stuff chiles with cheese and enclose filling by overlapping slit slightly if possible, then transfer to a plate. (Use a toothpick to mark any hotter chiles if desired.) Heat 1/2 inch oil in another 12-inch heavy skillet over medium heat until it registers 360°F on thermometer. While oil heats, beat egg whites with 1/8 teaspoon salt using an electric mixer until they just hold stiff peaks. Whisk yolks with 1/8 teaspoon salt in a large bowl, then gently fold in whites. Put flour in a fine-mesh sieve and dust chiles, turning them to lightly coat all sides. When oil is ready, dip chiles, 1 at a time (hold chile by stem), in egg coating, spooning it over chile to cover completely, then fry, turning once, until golden on all sides (lap oil over any lighter areas), 4 to 5 minutes. Transfer chiles with a slotted spoon to paper towels to drain. Meanwhile, reheat sauce over low heat. Lay chiles in sauce to serve.
PreparationRoast chiles: Roast chiles on their sides on racks of gas burners (1 or 2 per burner) over medium-high heat, turning with tongs, until skins are blistered and slightly charred, 4 to 6 minutes. (Or broil on rack of a broiler pan about 2 inches from heat.) Immediately transfer to a large bowl and cover, then let stand 20 minutes. Make tomato sauce while chiles stand: Purée all sauce ingredients except oil with 11/4 teaspoons salt in a blender until smooth, then strain through a medium-mesh sieve into a bowl, pressing on solids, then discarding them. Heat oil in a deep 12-inch heavy skillet or heatproof casserole (preferably one that can go to the table) over medium-high heat until it shimmers. Carefully pour in sauce and simmer gently, stirring occasionally, 10 minutes (sauce should still be thin). Season with salt. Stuff and fry chiles: Carefully rub off skins from chiles, leaving stems attached. Cut a slit lengthwise in each chile with kitchen shears, then carefully cut out seedpod (including attached ribs) without tearing chile (hotter chiles smell stronger when cut). Wipe chiles clean with a paper towel if necessary. Stuff chiles with cheese and enclose filling by overlapping slit slightly if possible, then transfer to a plate. (Use a toothpick to mark any hotter chiles if desired.) Heat 1/2 inch oil in another 12-inch heavy skillet over medium heat until it registers 360°F on thermometer. While oil heats, beat egg whites with 1/8 teaspoon salt using an electric mixer until they just hold stiff peaks. Whisk yolks with 1/8 teaspoon salt in a large bowl, then gently fold in whites. Put flour in a fine-mesh sieve and dust chiles, turning them to lightly coat all sides. When oil is ready, dip chiles, 1 at a time (hold chile by stem), in egg coating, spooning it over chile to cover completely, then fry, turning once, until golden on all sides (lap oil over any lighter areas), 4 to 5 minutes. Transfer chiles with a slotted spoon to paper towels to drain. Meanwhile, reheat sauce over low heat. Lay chiles in sauce to serve.