Hi Wayne
Good factual post, refreshing after all the recent rubbish advice and spam.
The lesson you learned
'Lesson for me - i need to continue cooking the gravy after the blending stage,
i have put some pre-made gravy in my slow cooker for the night to see the changes hopefully tomorrow'What they probably forgot to tell you about is the final boil. About 10-20mins.
The final boil and simmer, after blending, is fundamental to a good base gravy. IMHO ;D
On a rolling boil the base produces a froth, which turns into a bitter scum and is skimmed off as the oil starts to separate.
Then they turn it down to a very low heat ready for service and it sits there on the hob for hours.
Their not cooking it now, their just keeping it hot, so they can add it and make the curries.
So your slow cooker idea, isn't really what its all about.
The points you make in your OP are mirrored in my 3hr base video recipe.
http://www.curry-recipes.co.uk/curry/index.php?topic=5635.msg55692#msg55692Just a point about oil recycling.
Many chef's, whilst cooking the individual curries will spoon off excess oil from any particular dish, straight back into the curry base pot.
This is deliberate and just a normal cooking reflex. But quite a bit added flavour, when you think about it.
Looking forward to your Take Away Kitchen adventures

cheers Chewy