How to Make It
In a small skillet, combine the coriander seeds, cumin seeds and 2 tablespoons of the mustard seeds. Toast over moderately high heat, shaking the pan, until the seeds are fragrant and lightly colored, about 2 minutes. Transfer the seeds to a plate cool.
Transfer the toasted seeds to a spice grinder and grind to a coarse powder. Stir in the remaining 2 tablespoons of whole mustard seeds and store the spice mix in and airtight glass jar for up to 1 week.