01 - In a large bowl, combine ground chicken, egg, panko, green onions, soy sauce, mirin, grated ginger, garlic, salt, and black pepper. Mix until just combined—do not overwork the meat mixture.
02 - Wet your hands with water to prevent sticking and form the mixture into 16 evenly sized meatballs, rolling gently to maintain a loose texture.
03 - Heat vegetable oil in a large nonstick skillet over medium heat. Add meatballs and cook for 8 to 10 minutes, turning occasionally, until browned on all sides and cooked through to an internal temperature of 165°F. Remove from skillet and set aside.
04 - Wipe the skillet clean. In a small bowl, whisk together soy sauce, mirin, sake, sugar, cornstarch, and water until cornstarch is fully dissolved.
05 - Pour the sauce mixture into the skillet and bring to a simmer over medium heat, stirring constantly until thickened and glossy, about 2 minutes.
06 - Return the cooked meatballs to the skillet and gently toss to coat evenly in the sauce. Simmer for 2 to 3 minutes so the glaze adheres properly. Serve hot over steamed rice, garnished with sliced green onions and toasted sesame seeds.