Season the cutlets with salt and set up separate dishes of flour, beaten eggs and panko.
Coat each cutlet in flour, egg and panko, pressing lightly only where crumbs fail to attach.
Rest the breaded chicken for 8 minutes while heating 3/4 inch canola oil in a deep skillet to 350°F.
Fry two cutlets at a time for 3 to 4 minutes per side until the panko is golden and the center reads 165°F.
Drain on a rack and let the chicken rest for 4 minutes before slicing across the grain.
Whisk the ketchup, Worcestershire, soy sauce, brown sugar and mustard until the sugar dissolves.
Serve the sauce beside the sliced katsu or drizzle a narrow line over it just before eating.