For the freshest and tastiest garam masala, grind your own. Anything that is not used can be kept in an airtight container for later use.
The use of a mortar and pestle or this grind stone is often used in India because it is so easy to make things in small fresh batches. But a spice grinder or a designated coffee grinder will work great in your own kitchen.
Recipe by STIRR at http://makeastirr.com/grind-your-own-garam-masala/