Hi Jerry,
Couple of things to add to the discussion so far.
In terms of the chef's being able to recreate gravies at home and in smaller quantity, they can. The chef I work with at times does a market stall on the weekends. For this he knocks up a gravy at home the night before, he lives in a small apartment with well less then restaurant standard equipment. You can taste no difference in what he has made at home to what made in the restaurant.
Further to this, at the market stall he makes the buffet dishes ( he will make 3-4 curries for sale ) in an electric fry pan, and again they taste as good as if made in the restaurant. One time he had none of the whole spices to go in and it still tasted fantastic.
So certainly for Aussie indian curry style of things it is possible to do at home.
Now here is the big secret, and unfortunately it is not what we want to hear.
When he makes the gravy and the final dishes, he tastes it, and he knows what is missing or needed to fix it. He may have used a different brand of tomato puree which is more sour, or bottled garlic instead of fresh, or the cumin powder might have been roasted and is stronger etc.
Same with the onions, they might be stronger in flavor etc, but he with his expertise/experience knows what to do to correct it.
Unfortunately that is something that only comes with years of experience, I still have to get him to taste the gravies that I make following exactly the same recipe each time, but at times he will adjust things.
Hope that doesn't put too much of a dampener on things.
Cheers,
Mark