Sauce for Yakitori

This post is really more about the sauce than the yakitori.
Get as much chicken breast or boned chicken thigh as everybody is likely to eat.
Japanese naganegi (like a round leek) if available.
Cut meat into cubes a bit bigger than 1/2” and thread onto skewers, alternating with chunks of leek on some skewers. Leave enough room to hold the end of the skewer.
Grill, preferably over charcoal, and when a little charring is evident, pick up several skewers at a time and dip into the sauce below, allow excess to drip off a little and return to grill. Repeat until done.
Some skewers should be grilled just with salt, without sauce.

Tare or Sauce There are easier ways to make tare, but this is particularly tasty, and has a good consistency without being floury.
trimmings from chicken
ml mirin
ml soy sauce
2 spring onions, or green half of negi or dividing onion
chili pod
garlic clove
g demerara or raw sugar

Chicken trimmings - ideally about 4 wingtips, but any chicken part with plenty of skin, cartilege, and bone, but not much fat, is perfect.
Grill chicken trimmings and onion until some browning shows.
Bring mirin, soy sauce, garlic, and dried chili to the boil.
Stir in sugar.
Add chicken and onion.
Simmer for around 30 minutes - a larger batch will take around 2 hours to achieve a slightly gelatinous syrupy texture and plenty of chicken flavor.

Cool and store in a narrow glass jar - ready for dipping skewers of grilled chicken in.
Boil up "tare" after every use, and strain and add remaining tare to any new batch that you make up.