Pick out any dark bits from the agushi seeds.
Rinse the seeds in water about 2-3 times.
In a blender or a food processor, add the agushi seeds, half of the onion, and 1 scotch bonnet, and blend until fine.
In a large pan add about 4 tablespoons of palm oil and fry the agushi in it over low heat for about 8 minutes. Set aside.
Blend the tomatoes with the rest of the scotch bonnets.
In another pot, add some palm oil to cover the bottom of the pan, and then fry the sliced onions for about 2 minutes.
Add the blended tomatoes and cook for another 2 minutes.
Add the herrings, the koobi (see note 1), and the shrimp powder and stir.
Add a bit of water to the stew and leave to simmer for about 5 minutes.
Add the grouper chunks and the agushi and stir. Let it simmer for a further 5 minutes. See notes 2.
Serve with boiled yam, boiled ripe plantains, or plain boiled rice.