In a dry skillet, toast the coriander, cumin and fenugreek seeds, then grind them together in a spice mill. Combine with remaining ingredients and mix well.
This powder improves as it becomes better blended, the longer it is stored, It is best in about a month, but don't store it longer than 18 months.
A World of Curries by Dave DeWitt and Arthur Pais Isbn 0-316-18224-9 pg 212