01 - In a small saucepan, combine soy sauce, mirin, sake, sugar, garlic, and ginger. Bring to a gentle boil over medium heat, stirring until sugar dissolves. Reduce heat and simmer for 5 to 7 minutes, or until slightly thickened. Allow to cool.
02 - Thread chicken and spring onion pieces alternately onto the soaked bamboo skewers, distributing evenly.
03 - Brush the grill or griddle pan with vegetable oil and preheat over medium-high heat.
04 - Arrange skewers on the hot grill. Cook for 3 to 4 minutes on each side, brushing with tare sauce as they cook, until chicken is cooked through and beautifully glazed.
05 - Serve yakitori hot with additional tare sauce on the side, if desired.