Pound pork chops
Use a mallet to gently pound the pork chops to ½” thickness. Season with salt.
Prep the dredge
Set up the dredge for the pork. Add the flour to a shallow bowl. Add the eggs and 2 tablespoons of water to another and beat the eggs. In a third bowl add the breadcrumbs.
Add enough oil to reach at least 1” up the side of a cast iron skillet. Heat over medium heat until the oil is 350ºF (180ºC). Working one piece of pork at a time, coat the pork in the flour then the egg wash. Coat in the panko, pressing to adhere the breadcrumbs.
Fry the pork
Carefully lower the pork into the hot oil and fry until crispy and golden brown on the underside, about 1 minute. Use tongs to flip and continue to fry the pork, about another minute.
Remove to drain
Remove to a cooling rack set over a paper towel-lined baking sheet. Repeat with the remaining pork.
Prepare the cabbage
Add the cabbage to a small bowl and toss with the rice wine vinegar.
Assemble the sandwich
Spread some of the tonkatsu sauce over the bottom slices of bread then top each with a piece of pork. Drizzle more of the tonkatsu sauce over the top then top with cabbage and close the sandwich.
Serve the katsu sando
Cut in half or into thirds and serve immediately.