A natural flavour enhancer used in much the same way as garam masala is, this mix is quite often, quickly fried in hot oil/ghee and poured over the finished dish to deepen the flavour. This method is called tempering or tarka. I’ve heard it being referred to quite often as Bengali Five Spice.
1 tsp each of:
Brown mustard seeds
Kalonji/Nigella seeds – sometimes called onion seeds which are altogether different
Just combine them all together and keep in an airtight jar and store as you would other spices. Some people like to grind them before using, I prefer to use them whole. Used in Smoked Salmon Fish Curry.