Cut chicken thighs into bite-sized pieces and remove the skin. In a bowl, mix the chicken with soy sauce, sake, mirin, grated ginger, grated garlic, and 1 teaspoon of salt. Let it marinate in the fridge for 10 minutes.

Mix all-purpose flour and potato starch in a 1:1 ratio. After 10 minutes, let the excess marinade drip off each piece of chicken. Then, coat the chicken evenly in the flour mixture and gently shake off any excess.

Lightly grease a toaster tray with oil. Arrange the chicken pieces with space between them. Bake at 400°F (200°C) for 10 minutes, then flip each piece and bake for another 5 minutes.

Let the chicken rest for a few minutes after baking to allow residual heat to finish cooking the inside. Serve with a sprinkle of black pepper or a squeeze of lemon juice if desired.