In a dry sauté pan over medium heat, working with one spice at a time, toast cumin seeds, coriander seeds, fennel seeds, and ajwain until just warm and fragrant, taking care not to burn the seeds. Set each spice aside as it is done

In a high-powered blender or spice grinder, or using a mortar and pestle, combine all toasted spices along with dried mint, kala namak, salt, green mango powder, tamarind powder, black peppercorns, chili powder, and ginger powder. Grind to a fine powder. If using a spice grinder with a limited capacity, grind each ingredient in batches, then thoroughly combine in a small mixing bowl.

Store masala in an airtight container in a cool, dry place for up to 3 months. The masala's flavor is best the day after making, once the spices have had a chance to mingle. Enjoy!