01 - Combine soy sauce, mirin, sake, sugar, garlic, and ginger in a small saucepan. Bring to a boil over medium heat, then reduce heat and simmer for 8–10 minutes until the sauce thickens slightly. Remove from heat and strain out the garlic and ginger pieces.
02 - Thread chicken cubes and spring onion pieces alternately onto the pre-soaked bamboo skewers, ensuring even distribution for uniform cooking.
03 - Prepare a grill or grill pan over medium-high heat. Lightly oil the grates to prevent sticking and ensure proper searing.
04 - Place skewers on the hot grill and cook for 3 minutes per side. Begin brushing with the prepared yakitori sauce after each turn. Continue grilling, turning and basting frequently, for 6–8 additional minutes until the chicken is fully cooked and develops a glossy, caramelized coating.
05 - Remove skewers from the grill and serve hot. Drizzle with any remaining yakitori sauce for enhanced flavor.