Toast the sesame seeds on low-med heat on the stove for 5-10 minutes and then remove from the heat.
If using nori sheets, cut them in to strips about 2cm/1 inch wide. You can do them all at the same time by keeping them stacked. After cutting in to strips, cut again to form squares. Place them in the blender and gradually pulse them in to small flakes (say 2-3mm). Be careful as you don't want to turn it in to powder! This doesn't work in a food processor.
If you are using wakame pieces (larger than flakes), then you need to break these down by pulsing a little in the blender to about the same size (2-3mm).
Combine all ingredients in a clean glass jar and shake to combine.
Store in the pantry for up to 2 months.