Add chicken, toss well, and set aside to marinate for at least 15 minutes or covered in the fridge for up to a few hours.

Pour vegetable oil in the deep fryer and heat the oil and set it over high heat until the oil reached 180ºC.

Put the remaining 1 cup of cornstarch in a large mixing bowl. Lift half of the chicken out of the marinade, letting the excess drip off. Add it to the cornstarch and toss to throughly coat each piece. Do not shake off the excess cornstarch.

Use tong or chopsticks to add the chicken pieces one by one to the oil and fry, stirring and flipping the chicken occasionally, until it’s crispy and the visible meat is golden brown, about 6 minutes.

Make the sauce:

Combine the soy sauce, vinegar, mirin, sugar and sesame oil in a small bowl and stir until the sugar dissolves.
Just before you serve, stir in the scallion (spring onion) and shiso.