Chef & owner told me last week he wont cook more than 2 savoury curry dishes in the one pan when supplying & topping up his standard buffet for consistency of flavour. He just adds to it from single or double portions when needed.
He does do larger batches of korma / chasni, which require less "flavouring of the pan" . An English style tikka masala could also be done like this, but tm here in Glasgow is more often savoury than sweet. He sometime makes 5 or six curry dishes at a time when busy, so bulking for buffet is not really an issue for him.
For catering size portions he uses big pots, which end up good but different than the bir single portions.
Apart from garam masala, he never uses mix powders or powdered chilli in a dish as he reckons they are too harsh / hot & lack flavour when cooked in 10 mins or so.
I never had much success bulking up bir dishes, so after what he told me I wont bother now.
Regards
ELW