Just Bento

Yes, I do this at home. Just use a cornstarch slurry (cornstarch mixed with a little cold water or mirin or sake or whatever you like), adding a little at a time to a boiling mixture while whicking (this prevents lumpy bits). Once the bubbles coming up look thick and slow and syrupy (You'll see what I mean) then you are good to go. Remember though, the once your mixture is boiling, that is as thick as it will get, unlike a flour or roux based sauce that needs to boil a bit.

^ what red said! :)

Actually (food nerdiness alert) the other night I was reading up on 'teriyaki sauce' on some Japanese food site, and they said that bottled teriyaki sauce was actually an invention by Kikkoman, who developed it specifically for the U.S. / overseas market, to compete with other 'barbeque' sauces. There is or was no teriyaki sauce per se (though there are plenty of similar bottled sauces) in Japan, where teriyaki means a method of cooking with the 'sauce' being made in the pan with soy sauce, mirin, sugar, etc and coating the food. In fact, while the teriyaki method is written 照り焼き　(teriyaki), teriyaki sauce and food made from it is considered so 'western' that it's written in katakana, as all imported words are, like so: テリヤキ.

So... the bottled teriyaki sauces aren't really teriyaki sauce? :O Well, goodie I stuck to Maki's fantastic recipe, and didn't listen to my father who said I should take the bottled sauce at his shop (not that I would've had to pay for it, but still).