Preheat oven to 350 F. Spray a large baking sheet with nonstick cooking spray. Crush corn flakes. Combine crushed corn flakes with parmesan cheese and ranch dressing mix (any dry ranch mix will work) in a large bowl. Place beaten egg whites in a medium bowl. Dip each chicken thigh in he egg whites and then in cereal mixture to coat evenly. Arrange the coated chicken on the prepared baking sheet. Bake until golden brown and juices run clear when chicken is pierced with a knif, 20-25 minutes. Serve hot.