Grate the ginger and mince the garlic, then mix them with soy sauce, mirin, and sake (if using) in a bowl. Add the chicken thigh pieces and toss to coat them evenly in the marinade. Cover the bowl and refrigerate for about an hour to allow the flavors to soak in.

After marinating, remove the chicken from the marinade and lightly pat each piece dry with paper towels. Spread the potato starch in a shallow dish and coat each piece of chicken evenly, ensuring every part is well-covered for the perfect crispiness.

Pour a generous layer of vegetable oil into a frying pan and heat it over medium heat. Test the oil with a small piece of chicken to ensure it’s hot enough to sizzle.

Place the coated chicken pieces in the pan, making sure not to overcrowd them. Fry the chicken in batches, cooking for about 3–4 minutes per side or until golden brown and crispy. Adjust the heat as needed to avoid burning while ensuring the chicken cooks through.

Transfer the fried chicken pieces to a plate lined with paper towels to drain excess oil. Serve immediately with a side of lemon wedges or a sprinkle of Shichimi (Japanese chili spice mix) for an extra layer of flavor!