Slice the chicken meat thinly, then mince. Since it's tasty with a roughly chopped texture, there's no need to make it into a paste.
Mince the onion, and mix thoroughly into the meat together with the other ingredients.
Form the meatballs into your desired shape. Dampen your hands with a little water to form them into patties. I skewered mine.
5/15/12 note: They don't have to be grilled on skewers. Avoid getting the skewers gooped up with sauce by skewering after cooking!
To make the sauce: Add all the sauce ingredients to a pan and briefly simmer.
Simmer until the sauce boils down to almost half the amount, as shown in the photo in Step 5. If you over boil it, it will burn when cooking, so be sure to simmer lightly.
To grill the meatballs, pour sesame oil (not listed) in the pan, and grill both sides until golden brown.
Coat with teriyaki sauce, cook again and serve. Sprinkle scallions on top or your choice of garnish, and serve with Japanese mustard and mayonnaise.