I have often wondered why take away / restaurant curry can sometimes give you a dicky belly, while the ones cooked at home don't do this. I think it might well be that their gravy base could be hanging around for a few days, i.e fermenting.
I made a base on Monday, then left it until Wednesday morning before cooking a few curries. Though it hadn't started visibly fermenting flavor had noticeably improved (had a sour tang to it). I think its an important factor in the missing taste. Unfortunately, I didn't add enough oil to the gravy that there was enough to pour back into the base at the completion of each dish. I don't presently have a gas hob either, so I'm missing the flamed taste. Nevertheless, this is the closest I've been.
We know that most restaurants make their base sauce at least a day in advance. I can't believe they refrigerate it as the quantities are just too large. ( I doubt they'd be forthcoming in admitting this habit though, as it would flout food safety guidelines).