How to Make It
Thread each of 8 metal skewers with 3 pieces of chicken and 3 pieces each of scallion and shiitake.
In a saucepan, combine the soy sauce, mirin, kecap manis, sugar, ginger, Sriracha and garlic; bring to a boil. Simmer over low heat, stirring, until slightly thickened, 8 minutes.
Light a grill or preheat a grill pan. Brush the skewers with oil and grill over high heat, turning, until nearly cooked through, about 5 minutes. Brush the skewers with the sauce and grill, turning, until the chicken is cooked through and nicely glazed, about 3 minutes longer. Serve at once.