It is part of a neglected cooking process already mentioned on this forum, but quickly forgotten
Neglected & but not given much importance , I'm not sure if the process burns the spices slightly or just cooks them properly, I don't have the experience yet. It had been drummed into me about how easily spice burns & usually ended in a bottle job!
EDIT- the more I learn, I see a large % of the traditional bir process, the mass production of a fairly large menu, with as least fuss as possible...you could always 'singe' the spices into a homestyle curry, instead of adding them with a whole lot of other ingredients as is frequently called for
see the difference?
the real secret ingredient however, has been written on here, trouble is it was typed in white font

ELW