Skin the fish and cut into bite size
pieces. Chop the onion finely. Mix the onion, ginger, sherry, salt,
pepper and sugar together in a bowl. Put in the pieces of fish and
marinate for 30 minutes. Sift the corn flour and flour into a bowl.
Add the egg, 3 tbsp water and mix well. Dip the fish in this batter
and then in sesame seeds. Deep fry in hot oil until crisp and golden.