1. To make Tonkatsu: Slash white fat rimming of pork chop in several places to keep meat from curling or shrinking when deep-fried. Beat the pork chop with a meat pounder or a rolling pin to make them tender. Season both sides with salt and pepper.
2. Flour the pork chop lightly, dip in beaten egg, then coat with Panko. Use one hand for coating flour and Panko, and use the other to dip in egg to keep one of your hands dry.
3. Fry them in oil at 170C (340F) until cooked golden brown. (Turn the pork over to cook evenly.)
4. Remove the Tonkatsu from the oil and drain.
5. To make Katsudon: Cut Tonkatsu into small pieces. Slice the onion. Chop Mitsuba (Japanese wild parsley) into small pieces.
6. Put water, hon-dashi (dashi powder), soy sauce, mirin (sweet sake) in a pan and bring to a boil.
7. Add onion slices and simmer on low heat for a few minutes until tender.
8. Beat an egg, bring the soup to a boil, pour the egg over the onion, and lightly mix with chopsticks. Turn the heat down to low, add Mitsuba leaf (Japanese wild parsley), cover, and turn off the heat.
9. Serve steamed rice in a rice bowl, place Tonkatsu pieces, pour the simmered egg on top.
You can simmer the Tonkatsu with egg but to enjoy crispy Tonkatsu, I will simply pour the simmered egg over the Tonkatsu