Hi Jerry, thanks for your thoughts.
I honestly think that searching for the 'secret ingredient' within oil, is a red herring. It most definitely plays it's part and without it, we couldn't achieve that BIR aroma but it's what you add to it that creates the taste, and not what you add it to!
I also think that we have to be careful in trusting our noses when trying to identify 'that' aroma!
I have to admit, when I'm in the full throws of a BIR cooking session, I can not separate individual smells and it takes me at least a good hour to recover. Unfortunately, I have previously thought a curry left to stand, helps develop the flavour and the aroma, and to some extent, I would say that still stands but I'm leaning more towards the fact that the 'standing' time is more beneficial to me than it is of the curry. My senses recover and I can actually taste the dish in all it's glory.
Now, spoon off some of the oil made in that dish, and set it aside or in the fridge. Take it out and have a smell. To me, it absolutely smacks of that BIR aroma, so for me, the aroma is created at the frying stage and not so much in the base. I don't really subscribe to Julians theory of using seasoned (bhaji) oil, as I think the oil's flavour is too subtle to come through in a 10lt + size base. Of course, I will be in a better position to comment after my visit to c2g in June.
For me, it's spices (ground or whole) tempered in oil that creates the aroma with the addition of the garlic and ginger and of course, the onion contained in the base gravy. I just feel that as we are cooking our dishes, we don't always realise it.
Ray