To prepare the cabbage salad, separate the leaves from the head, and trim off the tough stems.
Roll a few leaves together and use a sharp knife to slice the cabbage into thin threads. Soak the cabbage in cold water while you prepare the rest of the ingredients.
Prepare two trays, one with a well-beaten egg and the other with the panko. Prepare a wire rack to drain the Tonkatsu Add 1 1/2-inches of oil to a heavy bottomed pot and heat the oil to 320 degrees F (160 C).
Salt and pepper both side of the pork cutlets.
Dust the pork with an even coating of flour.
Dip the cutlets in the egg and coat evenly.
Transfer the pork to the panko and mound the breadcrumbs around the meat, pressing down gently on the cutlet to ensure you get a good coating of breadcrumbs on all sides.
Fry the Tonkatsu until golden brown, flipping every few minutes to ensure even browning. Use a skimmer to remove any foam that accumulates on the surface of the oil. Depending on how thick your chops are they will take anywhere from 10-15 minutes to cook through.
You can test to see if they're done by removing one from the oil and inserting an instant-read thermometer into the center. It should register 140 degrees F (63 C).
When the Tonkatsu is done, drain it on a wire rack and let it rest for a five minutes before you cut into it.
While the pork rests, drain the cabbage and use a salad spinner to remove any excess moisture. Place big mounds of cabbage on each plate.
Slice the cutlets and plate with the cabbage. Serve with Tonkatsu sauce and Japanese mustard.