Having done a bit more reading i think one thing i missed was the initial caramelisation of the first ladle full of base sauce to get that deep colour. Also i did the small/fast batch of base sauce so im going to tweak that next time.
I will make the larger batch of base sauce but i think i will first roast the veg and peppers to get some extra flavour and sweetness out of them, then simmer it all together.
Like I mentioned before, seasoned oil might be one of the components that is stopping you getting the taste you want. You could do that but just remember the roasting affect is achieved by using high heat with aluminium pans and plenty of scraping.
Absolutely love BIR Curry, garlic chilli chicken is my favourite, the recipe from WizzFizz looks amazing! Need to try that! The only thing is I am so scared of cooking chicken, pathetic really I know, I always tend to over-cook it as I worry about it not being cooked through. So I tend to do beef curries more.
Well most takeaways will pre cook there chicken for curries for very reason you just said, no time to be worrying about if chicken is cooked through and letting it simmer lovingly in the sauce, BEFORE anyone says anything about "this is the real way to do a curry" Yes I know, but what were are talking about here is BIR.
I have had great results with pre cooked chicken, my fav method is to marinate the chicken in yoghurt, spices and garlic/ginger, then cook on highest heat in the oven. Fancy restaurants will cook there chicken in the tandoor then add that to the curry.
Other places will boil the chicken in oil, gravy and spices. I have also tried this method and have had good results with this also.
Another note on chicken, its not a good idea to simmer chicken breast in tomato based sauces, it goes rubbery, something to do with the acid, chicken on the bone is much better for this.