I will add to this as it seems to have evolved into a Vindaloo post but there are recent comments in some others as well... I didn't want to start another though.
I was looking for a Vindaloo recipe, prompted by putting items away 4 months ago (we moved house...for the last time, ever again!) and as I was putting the cider Vinegar away in it's new home, remembered that I used to really like the Vindaloo I made with it.. but I can't remember how or where I saw the recipe. That was another reason for my posting a few days ago, to see if I can find the recipe here maybe, as I used to read every recipe or near as.
Anyway, no luck but I did find this recipe, which I tried once but I can't remember if I really liked it or not (chicken on the bone is not really my thing).
https://niksharmacooks.com/chicken-vindaloo/What struck me earlier today was a post in the Vindaloo forum: Instant Pot and paneer vindaloo, once again discounting that 'missing ingredient' and about potato. I seem to remember someone suggesting that the Potato was an addition to the dish so that a server could distinguish the dish from other similar ones. As for the 'missing ingredient', it made me remember the above recipe and the 'Cooks comments' at the end, re stainless steel, which I don't really understand but maybe others do?
Having rechecked it today, I also delved into the comments and the author replies about the use of Cardamom which I also found interesting.
Consequently, I will have to retry his recipe again at some point and see if how it compares to other Vindaloo dishes I have made.
BAJ
P.S. Feel free to spilt this comment off it should have posted somewhere else - I may be a bit rusty.