Cut 300 g boneless chicken thigh(s) into bite size pieces.
Take a container and add 1 tbsp soy sauce, 1 tbsp sake, ⅛ tsp ground black pepper, 1 tbsp grated garlic and 1 tsp grated ginger root. Mix to combine and add the chicken pieces. Mix until fully coated and marinate in the refrigerator for 30 minutes.
While waiting for the chicken to marinate, add 1 tsp grated ginger root, ½ tbsp grated garlic, 1 tbsp soy sauce, 1 tbsp mirin, 1 tbsp sake, 1 tbsp honey, 1 tbsp water, 1 tsp rice vinegar and 1 pinch ground black pepper to a small sauce pan. Bring to a boil over medium heat, then lower to medium-low and simmer for 1-2 minutes. Set aside for later.
After 30 minutes, add 3cm (just over 1 inch) of cooking oil to a deep pan and heat to 160 °C (320 °F). While you're waiting for it to heat up, sprinkle about 5 tbsp potato starch onto a plate and take the marinated chicken from the fridge. Coat each piece evenly with starch, making sure to shake off the excess marinade before coating.
Once the oil is hot, add the chicken pieces and fry for about 3 minutes on each side.
Increase the heat to 190 °C (374 °F) and fry for 1 minute on each side.
Transfer to a wire rack to drain excess oil.