What are " sizzling seeds"? (for curries)

black mustard seed

I just made Panfusine's Mung and Quinoa Crepe. The potato masala starts with cumin and mustard seeds in hot oil "until "the mustard seeds sputter and cumin seeds split" -- they smell fantastic and just kick up all the senses!

For a many curries, you add something called "tempering spices" towards the end of cooking. These are usually spices such as whole cumin seeds and mustard seeds that are fried in oil until toasted before you add them to the curry itself. This process finishes off the dish, and adds a lot of flavor, sort of rounding everything out.

Probably seeds--mustard seeds, for example--fried in some oil until they begin to pop.