Peel the onions and slice them thinly.

Heat the peanut oil to 150 degrees Celsius (302 degrees Fahrenheit) in a heavy-bottomed pan/pot and fry the onions in it for a few minutes. They should become crispy and gain a bit of color.

Take them out of the oil and let them cool on absorbent paper - e.g., a clean dish towel or paper towel.

Blend the seaweed, bonito flakes, salt, and half of the sesame seeds. Use either a blender, mini chopper, or spice grinder for this.

Put the cooled onions in the blender and blend them briefly. They should not be finely blended.

Finally, add the remaining half of the sesame seeds, and the mixture is ready.