In a bowl, whisk the egg. In another bowl, mix the Panko crumbs, flour and salt together.
Dredge the chicken pieces in the egg, shaking off the excess. Then set the chicken in the Panko mixture and flip it a few times to thoroughly coat the outside.
Using a heavy and deep skillet or dutch oven, pour the cooking oil into the pan until there is a solid layer of oil in the bottom, about 1/8 inch high. The oil needs to be heated to and stay at 350 degrees F for the perfect fry.
When the oil reaches 350 degrees, add the chicken and cook on each side for 5 minutes or until the Panko looks golden brown. When the internal temperature of the chicken reaches 165 degrees F, remove the chicken to a wire rack. Season with salt.
To assemble the sandwiches, add sauce to the bottom bun, then add the chicken and top with cabbage, cilantro and more sauce, as desired.