Run Bonito flakes through a mini food processor or finely chop, place in a mixing bowl and set aside.
Blitz sesame seeds and crushed chilies (if using) a few times in mini food processor, just enough to break them up a little. Note: This is optional.
Add sesame seeds and crushed chilies to a small nonstick pan. Toast over low heat until fragrant. Remove from heat, and add to the bowl with bonito flakes.
Add remaining ingredients to the bowl, stir well to combine.
Allow mixture to cool to room temperature before transferring to an airtight container.
