Cut the red cabbage into eighths and finely shred or slice one eighth. Place it in a medium-sized bowl and marinate with rice vinegar, sesame oil, and salt. Set aside.
Detach 4 leaves from the head of lettuce and wash thoroughly. Pat dry and set aside.
Halve the chicken breast lengthwise, then cut each half again crosswise. Place each piece between two layers of plastic wrap and pound to about 0.5 cm / 0.2" thickness using a meat mallet. Lay the flattened meat on a plate.
Set up a breading station with three shallow dishes or bowls. Fill the first dish with 1.5 heaped tablespoons of wheat flour, crack an egg into the second dish and whisk it. In the third dish, mix together 3 heaped tablespoons each of panko and breadcrumbs. Coat each piece of chicken first in flour, shaking off excess, then dip in the egg, and finally, press into the breadcrumb mixture, ensuring it's well coated on all sides. Place the breaded pieces side by side on a plate.
Heat clarified butter in a large frying pan and fry the breaded chicken pieces on both sides until crispy, about 3 minutes per side or until cooked through. Let the meat drain on kitchen paper.
Place half of the slices of bread flat on a clean work surface, then place a lettuce leaf on each. Top each with a piece of cooked chicken, followed by a zigzag pattern of Kewpie mayo and Tonkatsu sauce. Add about 2 tablespoons of red cabbage salad on top of the sauces. Finally, top the sandwiches with another slice of bread. If desired, trim the edges all around and cut the sandwiches in half in the middle with a sharp knife.
Notes
The calorie information may vary depending on the product used, country and region.
