1. On a chopping board, stuff poblano chiles with Oaxaca cheese and secure with toothpicks. Place egg whites in a bowl. Using a hand mixer, beat egg whites for 5 minutes or until they double in volume. Toward the end, gently fold egg yolks into egg whites. Coat each Poblano chile with flour and dip in batter.
2. In a pot over medium heat, heat plenty of vegetable oil. Working one at a time, deep-fry each Poblano chile for 5 to 8 minutes or until golden brown. Continuously spoon hot vegetable oil over the battered chiles to keep them hold their shape. Drain on a paper towel-lined plate and set aside.
3. In a blender, combine tomatoes, garlic, onion, chipotle chile, salt, pepper and chicken broth and blend for 5 minutes. Pour the sauce into a pot, cook for 10 minutes and set aside.
4. Serve cheese chile relleno spooned over with chipotle sauce and garnished with cilantro leaves.