If you can't find mirin in your grocery store's Asian foods aisle, substitute 1 tablespoon sugar dissolved in 1/2 cup rice wine vinegar or vermouth.
Soak skewers in water 30 minutes. Preheat grill to medium-high heat (350° to 400°).
Combine mirin and next 5 ingredients in a small saucepan over medium-high heat. Bring to a boil, and cook 10 minutes or until slightly thickened and reduced to about 1/2 cup. Let cool. Reserve 3 tablespoons glaze.
Thread chicken and green onions evenly onto skewers. Brush skewers with soy glaze.
Grill skewers 4 to 5 minutes on each side. Brush with reserved soy glaze before serving.
Delicious, easy and a nice way to use chicken thighs and/or breasts from the freezer. I used a combo of both thighs and breasts and it was great.