Cut 350g of boneless chicken thighs into 2 × 1½in / 5 × 4cm pieces. Toss with 1 tablespoon of soy sauce, 1 tablespoon of sake, ½ teaspoon of mirin, and 2 teaspoons of grated ginger with its juice.
Marinate for 30 minutes to 1 hour. Pat dry with paper towels, sprinkle with 20g of cornstarch, and turn to coat every piece.
Heat 1½in / 4cm of vegetable oil in a deep pot to 320°F / 160°C. Fry the chicken in batches for 2½-3 minutes, then drain and rest for 3-4 minutes.
Heat the oil to 375°F / 190°C. Fry the chicken again for 30 seconds to 1 minute, until golden brown and crunchy and it reaches 165°F / 74°C.
