Shell the eggs and crush using the back of a fork.
Mix the eggs with the rest of the ingredients for the tartar sauce.
Set aside.
Cook the marinade
Boil together the ingredients for the marinade until the sugar dissolves.
Pour into a shallow bowl and cool.
Cook the chicken
Sprinkle the chicken with salt and pepper. Toss with the potato starch.
Heat the cooking oil and fry the chicken, in batches, until golden brown and cooked through, about two to three minutes per side depending on the thickness.
Marinate the chicken
Place the cooked chicken in the marinade in a single layer. Allow to soak for half a minute to three minutes per side.
Assemble the chicken nanban
Arrange the chicken pieces on a plate (leave the excess marinade behind) and spoon the tartar sauce beside them.
Sprinkle with toasted sesame seeds and scallions before serving.