it doesn't transform a home made Curry into a BIR Curry.
On it's own, it doesn't
But I have seen it in a takeaway
It is used as the curry powder part of the "restaurant spice mix"
There are loads of different makes and they are not all hot
The one I use is no hotter than a standard "East End" Madras curry powder
The ingredients are:-
paprika,turmeric,coriander,garlic,cloves,fenugreek,mustard,ginger,chilli,black cardamom,curry leaf,fennel,cummin,black pepper,ground cinnamon,edible oil
I bought a "small" 400 gramme pack, but it also comes in wacking great catering packs too.
I wouldn't make the assumption that all curryhouses use it, but certainly one does