Combine Worcestershire sauce, ketchup, soy sauce, oyster sauce, Dijon mustard, and sugar in a small bowl. Whisk until the sugar dissolves and the sauce is smooth. Taste and adjust with a little more ketchup if you want it sweeter. Set aside.

Place each chicken breast between two sheets of plastic wrap or in a zip-lock bag. Pound with a meat mallet or the flat base of a heavy pan until the thickness is an even 1 cm throughout.

Season both sides of each breast with salt and black pepper.

Set up a breading station: flour in the first shallow dish, whisked egg mixture in the second, and panko breadcrumbs spread in the third.

Working with one piece at a time, dredge the chicken in flour and shake off any excess so only a thin, even layer remains.

Dip the floured chicken into the egg mixture, letting the excess drip off.

Press the chicken firmly into the panko on both sides, patting with your palm so the breadcrumbs adhere in a compact, even layer. Place the coated cutlet on a wire rack and repeat with the remaining pieces.

Let the coated cutlets rest on the rack for 2 minutes before frying.

Pour oil into a large, heavy-bottomed skillet to a depth of about 1.5 cm. Heat over medium-high until an instant-read thermometer reads 175 C / 345 F.

Carefully lower two cutlets into the oil. Fry for 3 to 4 minutes on the first side until deep golden brown, then flip and fry for 3 to 4 minutes more until the second side matches and the chicken is cooked through to 74 C / 165 F internal temperature.

Transfer the cooked cutlets to a clean wire rack set over a sheet pan. Do not stack them. Fry the remaining two cutlets, checking that the oil temperature returns to 175 C before adding them.

Slice each katsu crosswise on the diagonal into 2 cm strips. Arrange over steamed rice with shredded cabbage alongside. Spoon or pour tonkatsu sauce over the cutlet just before serving.