Slice the chicken breast diagonally into bite-sized pieces. Place in a bowl, season with salt, pepper, and sake, and massage. Let sit for 5 minutes, then coat with cornstarch.

Cut the chives into 4cm lengths and thinly slice the green onion.

In a separate bowl, mix the sauce ingredients (sugar, vinegar, soy sauce, sesame oil, garlic, and sesame seeds). Add the chives and green onion, and mix well.

Heat vegetable oil in a frying pan over medium heat. Add the chicken and cook for 3–4 minutes, flipping occasionally until fully cooked.