The triple cook recipe certainly produces a crispy chip. Though I am struggling to accept that the chip that daveeb is searching for would actually be bar Boiled or even roasted. But then, we wouldn't normally have chips with a curry in my area so would expect to find frozen being used.
Commercially the frozen chip market is huge, so I would start my search there I feel. The sweetness you mention Dave, do you think it might be from the cooking of chips they would use for bhaji etc. perhaps that is where the sweetness is imparted.
These are just my thoughts on it, sorry I can't be or more help, good luck with your quest. Perhaps you could take some pics next time you get some?
Cheers,
Malc.