Cut onion and green onion into small pieces.
In a medium bowl, add ground chicken and salt. Mix it all up until there is stickiness.
Add grated ginger, potato starch (or Katakuriko), mayonnaise, and bouillon, freshly ground black pepper, sake, and soy sauce in the bowl. Mix them all up!
Add onion and green onion to the bowl and mix well.
Form the mixture into about 4 inch size long pieces or 2 inches small circle shaped.
Prepare a baking pan with parchment paper and put the pieces in the pan.
Set oven to 400F° (205C°) and cook for 17 minutes. please put the pan on the second rack in the oven.Check and open the oven after 10 minutes. After the timer goes off, take out the baking pan from the oven and now let's make Yakitori sauce.