Cut the chicken in large pieces and mix with soy sauce and sake. Marinate for 5 minutes.

Mix soy sauce, sake, rice vinegar and sugar together in a bowl.

Heat the oil in a frying pan and lightly sauté the minced leek and red chilli. Then add the sauce to the pan, stirring constantly. When the sugar has dissolved take off the heat and set aside.

Remove the chicken from the marinade and coat thoroughly with potato starch.

For the best results, the chicken should be at room temperature before deep frying. Deep fry the chicken at a medium high temperature (170- 180ºC), making sure each piece is completely immersed in the oil so that it cooks on the inside while remaining crispy on the outside.

Remove when golden brown, drain. Place on a serving plate and cover with the leek sauce.