Add the cassia bark, the nutmeg, the whole cloves, and the allspice berries to a spice grinder, and then grind these into a fine powder. This should take between 15 to 30 seconds.
transfer the powder to a small bowl, then add the ground ginger into the rest of the powder and throughly combine.
Transfer the finished pumpkin pie spice blend to an airtight container and store in a cool, dark place.