If you do (plan to) use mustard oil in BIR, don't forget to take it up to smoking point and then back it off; it both improves the flavour and destroys the harmful ingredients that normally cause it to be labelled "for external use only" (erucic acid).
** Phil.
Well I can't find her video now, but quite a while back I came across an Pakistani woman (youtube video) who didn't use mustard oil in her cooking, but she did include Colman's dry mustard powder into her recipe somewhere to get the mustard flavour, I'll have another look and if I come across it again, I'll link it.