In a bowl, combine soy sauce, sake, mirin, minced garlic, and grated ginger. Add the boneless chicken thighs and mix well to ensure the chicken is fully coated. Cover and marinate in the refrigerator for at least 30 minutes.

Prepare the Coating

In a separate bowl, mix cornstarch, all-purpose flour, salt, and black pepper. Set aside.

Coat the Chicken

Remove the marinated chicken from the refrigerator. One piece at a time, dredge the chicken in the flour mixture, ensuring it is well coated. Shake off any excess flour.

Heat the Oil

In a deep skillet or pot, heat the vegetable oil over medium-high heat until it reaches 170°C (340°F).

Fry the Chicken

Carefully add the coated chicken pieces to the hot oil in batches, ensuring not to overcrowd the pan. Fry for about 5-7 minutes or until golden brown and cooked through. Remove the chicken and drain on paper towels.

Serve

Serve hot as is or with a dipping sauce of your choice. Enjoy your Chicken Karaage!