Slice the chicken breast horizontally into two pieces. Season with salt and black pepper, and let it stand for 10 minutes. Mix all the ingredients for the Katsu Sauce in a bowl and stir to combine.
Heat a pot of cooking oil for deep-frying. The ideal temperature is about 350°F (180°C).
Dip each piece of chicken into the beaten egg, then immediately coat it with panko. Shake off the excess. Dip the chicken into the egg again, then coat it with panko for a second time, ensuring it is evenly coated with a thick layer. Repeat the process for the other piece of chicken.
Once the oil is fully heated, gently drop each piece of chicken into the pot and deep-fry until both sides are golden brown. Remove the chicken and place it on a plate lined with paper towels. Cut the chicken into strips and serve immediately with steamed rice and katsu sauce.
Video
Notes
You can buy the bottled Katsu Sauce or Tonkatsu Sauce from Japanese or Asian food stores.