Make the chicken: Heat oven to 400 degrees F. Line a rimmed baking sheet with nonstick foil. Place the cornflakes in a shallow bowl.
In a large bowl, whisk together buttermilk, ¼ teaspoon salt and Cajun Seasoning; toss with chicken. Coat chicken in cornflakes, pressing gently to help them adhere, and place on the prepared baking sheet. Bake until cooked through, about 15 to 20 minutes.
Meanwhile, make the waffles: In a medium bowl, whisk together flour, baking powder, baking soda and salt (a dash).
Using an electric mixer, beat 2 egg whites (keep yolks and set aside) until stiff peaks form, 2 to 3 minutes; set aside.
In a large bowl, whisk together 2 egg yolks and buttermilk. Add flour mixture, stirring just until incorporated. Gently fold in whites until no streaks remain.
Working in batches, drop spoonfuls of batter (2 tablespoons each) on a waffle iron and cook according to manufacturer’s instructions until golden brown.
Form sandwiches with waffles, chicken, apples (optional) and maple syrup.