01 - In a small saucepan, combine soy sauce, mirin, sake, sugar, garlic, and ginger. Bring mixture to a gentle boil over medium heat, stirring regularly until the sugar dissolves. Lower heat and simmer for 5 to 7 minutes until the sauce slightly thickens. Allow to cool completely.
02 - Thread chicken pieces and spring onion segments alternately onto soaked bamboo skewers, ensuring pieces are evenly spaced for uniform cooking.
03 - Lightly brush the grill or griddle pan with vegetable oil and preheat over medium-high heat until hot.
04 - Place assembled skewers onto the preheated grill. Cook for 3 to 4 minutes on each side, turning once and brushing generously with tare sauce while grilling. Continue until chicken is cooked through and lacquered with sauce.
05 - Transfer skewers to a serving platter. Serve immediately with extra tare sauce on the side if desired.