If I can offer the perspective of a newcomer, this thread is embarrassing.  But if this has to go ahead, could I nominate myself in the loser category?

What a beauty! We don't buy SR flour as plain is much cheaper here and you can just add some baking powder.  Which your naan proves in reverse

If you start with a good raw ingredient, I think it's pretty hard to end up with tough chicken - it is very forgiving, and very flexible as the wide variety of different cooking methods on this thread show.
This is not an easy subject, but a lot of BIRs use chicken that has been bulked by injection with protein/brine solution. It not only inflates the meat-packer's profits, but results in a tenderized product.
I don't like the idea myself. We buy chicken in bulk from a wholesalers and I have checked carefully on the labeling for any indication of pre-treatment - there is none. (The chicken happens to be Halal, by the way, which is interesting because the wholesaler is for the French restaurant / catering market, which is not widely noted for its use of Halal meat.)
Our method is simply to fry off some minced onion/ginger/garlic in quite a lot of oil and cook the chicken chunks with a little gravy, haldi, bay leaf, mix powder and salt.  It fries at first but then develops a liquor. We cook for 8 mins past this point then leave it to rest with the lid on for 20 mins. Our temperature guide is to exceed 80C for 10 mins.  We don't add any liquid other than a little gravy as that just ends up making a soup.

Interesting thread this - and there are probably as many answers as there are chefs. The first place I worked in pre-cooked the chicken / lamb and then reduced the cooking liquor to a stodge that they then tipped into the cooked meat. If you ever scraped a pan with a spoon, this was heaven.  I tried it myself but kept catching the stodge on the pan, so now we just keep the protein in the cooking liquid and spoon a chef's spoon of the liquor into each portion. The enhancement to the flavour of the sauce is considerable - so much so that we now add veg stock to some vegetarian dishes to build up the umami in the same way.
Which brings me to not one but several occasions on which I have asked chefs what they do with the pre-cook liquor, to be told that it goes into the gravy. I once asked if this might be an issue for the dishes on the menu with a green "V" against them, and he replied "Makes vegetarian taste better." Hmmmm.....
I have heard stories of it being poured down the sink but can't say I have seen this. If true it's a terrible waste.

That's true. A restaurant owner I knew used to moan about his chef using too much spice. It was a time when a lot of costs were rocketing. I used to tease him that if he used any less spice he might as well reopen as a Chinese takeaway. During the 6 months that I worked there (Redhill) the quality and flavour level of the cooking dropped considerably. When I went back some time later, he had sacked the chef and replaced him with one of his family. The food was not very good and was available on buffet only. A year after that his email account starting bouncing and when I asked after him, I was told he had done a runner back to Pakistan. Last time I saw the place, the tables had been ripped out and it was a takeaway selling chicken in a bucket
So don't skimp on the spices and oil folks.

I think the oil gets incorporated into the sauce - emulsified I guess. We use a lot of oil in our gravy, but only a little of it sits on top, so it must be in there somewhere. How much of it splits back out when you cook in the pan I have no idea.

Great pics SP - they really made you welcome. Nice work.
Tim

Tomato in the gravy - I'm not a fan. But then I prefer a Bangladeshi old-style curry such as you got in the London area in the 1980s (and often still do in Brick Lane and South London.) The high tomato content is more of a Pakistani / Punjabi thing.  Glasgow curries tend to have a lot of tomato in the base, for instance. But I find it too sharp. All a matter of taste of course.

Despite the fact that I make a ridiculously complicated gravy, I agree totally with N.O. Years ago I had been pestering a local chef for his gravy recipe for months and eventually he got exasperated: "100 time you ask me and 100 times I say onions, cabbage, spices and oil. That's it!"
I now realize that a good chef can make a good curry with a simple onion gravy. The reason I persist with my complicated gravy is more to do with superstition - it works so I don't want to change it.

When I first moved to France I had endless problems trying to get onions as sweet as the Dutch ones we used to get from the Indian wholesaler in the UK. I even tried growing my own!  But we found that simply cooking the gravy for longer solves the problem.  Soaking in water is worth a try too though, N-O - thanks.