In a large mixing bowl, add the chicken mince, finely chopped spring onions, egg, grated ginger, bread crumbs, and chopped shiso leaves if using. Use your hands to knead the mixture until it becomes pale, smooth, and well combined, ensuring all ingredients are evenly distributed.

Wet one hand with water to prevent sticking. Scoop 1 to 2 tablespoons of the mixture using a spoon, then gently shape it into a ball with your fingers. Carefully press the skewer through the meatball until it reaches about two-thirds of the way down the skewer. Smooth out any rough edges for a neat appearance.

Repeat the scooping and shaping process to add another 1-2 meatballs onto each skewer, making sure they are spaced evenly.

Heat vegetable oil in a large frying pan over medium-high heat. Add the meatball skewers and cook for 2-3 minutes on one side until browned. Flip and cook for another 2-3 minutes until the meatballs are cooked through and golden on all sides. Remove the skewers from the pan and set aside.

In the same pan, combine soy sauce, cooking sake, and sugar (or use teriyaki sauce). Bring to a boil, then reduce heat to low. Return the skewers to the pan and baste the meatballs generously with the sauce. Cook for 1 minute, flip the skewers, and baste again to coat all sides, allowing the glaze to thicken slightly around the meatballs.

Remove the glazed meatball skewers from the pan and serve immediately while hot, either on their own or with steamed rice and vegetables.