Cut chicken into bite-sized chunks and place in a bowl with the soy, mirin, sake, sugar, garlic and ginger. Stir well to coat the chicken and leave to marinate for 20 minutes (overnight is fine too). Add water where necessary.
Cut the white part of the spring onion into 3cm pieces. Reserve the green part.
Thread a piece of chicken onto the skewer, followed by a piece of spring onion. Keep adding until you have use all the chicken and spring onion, you should make 2 skewers each
Heat a frying pan on medium heat with a little oil. When the oil is hot, place the skewers in the pan and cook until both sides are brown, about 5 minutes on each side. Reserve the remaining marinade.
Then, add the remaining marinade plus water, cover with a pan lid and cook on a low heat for 2–3 minutes until the sauce thickens in the pan and chicken is tender.
Serve with Japanese Slaw and shredded spring onion