From America's Test Kitchen. (I haven't tried it yet.)
2 nori sheets, toasted* and torn into roughly 1" pieces
3 T toasted sesame seeds
1.5 T bonito flakes
1.5 t sugar
1.5 t flaked sea salt
Put nori in a spice grinder and process until pieces are ≤ 1/2".
Add sesame seeds, bonito, sugar and salt. Pulse until nori is ≤ 1/4" (about 2 pulses). Store in a glass jar.
* You want 2 sheets the size you'd use for rolling sushi, though you could certainly swap in 6-7 of the small snacking sheets (which probably wouldn't need to be toasted).
To toast nori, turn on a stovetop element and wave the nori about 2" above the hot element. Start farther from the element and move the nori quickly at first and then come in closer and/or slower. You'll have to change the side you hold to toast the whole sheet. Signs that it's getting toasted:
--it gets a little wrinkly
--you see a slight color change (deep green to deep greeny-purple) if you hold it up to a light
-- it gets more brittle and easier to tear into pieces
