Combine the flour, cornstarch, pepper and salt and sift together onto a plate or piece of waxed paper.
Beat the egg yolk and water to a smooth cream then incorporate the flour mixture a few tablespoons at a time.
Just before using the batter, beat the egg white until stiff enough to stand in peaks when lifted on the beater.
Scoop the egg white into the batter and fold it gently with a spoon or spatula.
Heat the oil in a deep heavy pan.Pat the fish fillets dry with paper towel.
Pick up fillets with tongs and dip into batter and carefully drop into the hot oil.
Deep fry for four to five minutes, turn them as they brown. This will require about three minutes.
After they brown, transfer the fillets to paper towel to drain excess oil.