Many Indian dishes begin with whole mustard seeds fried in oil along with curry leaf. Besides imparting the oil,  and every subsequent ingredient that passes through the oil with a pungent mustardy flavor, the seeds themselves become a nutty, toothsome delight in the finished dish. The ground seeds form a slightly oily powder that’s the basis for the condiment mustard, but it can also be used in any powdered seasoning blend, marinade or dry seasoning rub.