Mix together the egg white and the water in a deep plate.
Mix together the flour, cornstarch, salt and pepper on a piece of waxed paper.
Roll each piece of fish in the egg white mixture, then in the flour.
Preheat a browning dish (Corning) 6 minutes at HIGH.
Without removing the dish from the oven, add the oil.
Place the fish pieces in it one next to the other and press them down with a fork for perfect contact with the dish.
Brown 6 minutes at HIGH.
Turn carefully and let stand 6 more minutes in the oven, without heat.
Place on a hot plate, browned-side up.
Place butter and capers or gherkins in a micro wave-safe dish.
Microwave 1 minute at HIGH.
Pour over fish.