Also known quite commonly as Bengali 5 spice. A natural flavour enhancer used in much the same way as garam masala, panch phoron is a whole spice mix, made up of seeds in equal portions. Typically, these seeds, as you can see will be fenugreek, fennel, cumin, black mustard and nigella.
My granny would always make it up as she needed it, and I do the same. Quite often, panch phoron is quickly fried in hot oil/ghee and poured over the finished dish to deepen the flavour. This method is called tempering or tarka.
The term “panch phoron” literally means 5 spices, “panch = 5”.
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. On this site, it’s used in the Smoked Salmon Curry, amongst other recipes: