Clean and wash the gizzards thoroughly. Season with the salt, pepper, seasoning cube,and onions.On medium heat; bring seasoned gizzards to boil in a small pot for about 20-30mins. Drain excess water and let cool. Lightly oil the gizzards with butter or oil.Place oiled gizzards in a baking pan lined with foil paper; broil or grill on high heat for about 1 minute or until slightly browned.Set aside to cool.Break the egg and pour into the blender.Wash the plantain; peel off the skin. Cut into chunks and put into blender as well. Blend on high speed for about 15 seconds or until the mixture is smooth. Add breadcrumbs, and any other spice you desire. Blend again for about 5 seconds.Pour plantain batter into a medium sized bowl; add the chopped fresh herbs; mix well with a fork.Pour the gizzards into batter and allow them to coat properly. Fry in a large frying pan for about 2 mins or until gizzards are golden brown all round.Serve immediately with your favourite sauce or just on its own.