Japanese
Cut the chicken thighs into 4-5 cm pieces, leaving the skin on.
Mix the soy sauce, sake, ginger, garlic and sugar in a bowl, add the chicken, toss well and marinate in the fridge for 30 minutes.
Drain off any liquid that has not been absorbed, then coat each piece in potato starch and shake off the excess.
Heat the oil in a deep pot to 170C and fry the chicken in batches for 3-4 minutes, until pale golden; lift out onto a rack and rest for 4 minutes.
Raise the oil to 190C and fry the pieces again for 1 minute, until deep golden and crisp.
Drain on a rack or paper towels for a minute.
Serve hot with lemon wedges to squeeze over.