1Combine the soy sauce, mirin, ginger, sugar, pepper and sake in a small saucepan over medium heat. Bring to a simmer, stirring occasionally to dissolve sugar. Simmer for 3-5 minutes until marinade thickens slightly. Set aside to cool.
2Place the chicken and mushrooms into separate bowls then pour 2 tbs of the soy marinade over the chicken and the remaining over mushrooms, stir to coat. Cover and refrigerate for 1 hour or longer if time permits.
3Drain the chicken, discarding the marinade. Thread the chicken, mushrooms and green onions onto skewers.
4Preheat a barbecue grill or plate on medium heat. Cook the skewers, turning and basting occasionally with marinade from mushrooms for 12-15 minutes or until chicken is cooked through.
5Serve with cabbage salad and/or rice.