Place a skillet over medium-high heat. Add minced ginger and onion, stir and saute until it's brown but not burn, it took about 15 minutes or more. If you think it's burning reduce the heat. Sprinkle salt over the onion to get the water out of it.
Sorry, I don't have the picture after it was caramelized.
Add the remaining ingredients except for the fish and salt. Continue to stir so it doesn't burn. Cook for about 10 minutes or more. You don't want any liquid in the mixture.
Debone the fish and add it to the mixture and continue to stir, add salt and continue to stir. Check for the seasoning and readjust. Take it off the heat, let it cool and stuff the plantains
If you like it spicy, add some when you add the other ingredients and cook along together.