Rinse the chicken wings and wipe dry. Season with salt and pepper. Set aside.
In a wok, heat the sugar, soy sauce, sake, mirin, ginger and garlic. Allow to boil gently over medium heat, uncovered, for a minute. Turn off the heat. Set the sauce aside to cool.
In another wok or frying pan, pour in enough cooking oil to reach a depth of at least three inches. Set the heat to medium.
Wipe the chicken wings once more. Add the potato starch to the chicken and toss to coat each piece with a thin layer of starch.
Fry the chicken wings in batches just until lightly browned. Transfer to a strainer as they cook, go on to the next batch, and so on.
Turn the heat to high. Fry the chicken wings again, this time, in smaller batches of four or five (see the difference after the first and second frying).
Dump the cooked chicken wings into the pan with the sauce. Toss to coat each piece of chicken with sauce.