Marinate the chicken in a non-reactive mixing bowl: combine the crushed ginger and garlic, soy sauce, sake, sesame oil, sugar, and chicken drumettes, and set aside to marinate for 20 minutes.
Make the cucumber cabbage salad: slice the cucumbers, sprinkle salt on them and set them aside; in a large bowl, combine the shredded cabbage, scallions/spring onions, grated fresh ginger, roasted seaweed, and sesame seeds. Make the dressing by combining Shichimi Togarashi Japanese Seven Spice, sesame oil, soy sauce, rice vinegar, and mirin. Squeezed the sliced cucumber of excess liquid then add it to the salad, pour on the dressing, combine everything, taste, adjust seasoning if needed, then pop it in the fridge so the flavours meld and cabbage softens.
Return to the chicken: spread the potato starch, salt and pepper out on a tray. Shake the marinade off the chicken to remove any ginger or garlic pieces. Roll the chicken in the potato starch mixture, ensuring all the pieces are fully coated before placing them in the fridge for an hour. If you have leftover potato starch apply it to the chicken as the chicken will absorb the potato starch.
Put the rice on to steam in a rice cooker. When it’s done, use a fork to fluff it up, close the lid, and leave it until you’re ready to assemble your rice bowl.
Finish the chicken: heat the oil in a deep fry pan or deep fryer to 165°C (330°F). Give the chicken pieces a light shake before adding them carefully to the oil. Do not crowd the pan; if the pan is small, cook the chicken in batches. Fry for around 2 minutes, after which the chicken should have a pale brown colour. Transfer the pieces to a wire rack and repeat until all the chicken pieces have been cooked. Remove any loose pieces of coating from the deep fryer as these may burn at a higher heat.
Increase the heat to 180°C (355°F) and re-fry the chicken pieces for a minute per batch. The chicken should be a light golden brown with a crispy skin. Check that the chicken has reached 74°C (165°F) then transfer the pieces to the wire rack again.
Assemble the dish: distribute the steamed rice between bowls; use tongs to transfer the chicken pieces to the bowls; drop a couple of generous scoops of cucumber cabbage salad beside the chicken; sprinkle on some sesame seeds, sliced roasted seaweed and bonito flakes, and squirt on some Kewpie mayonnaise. Serve immediately – with sake or Asahi.