Sift the flour and salt into a bowl and make a well in the middle. Add half of the beer along with the whole egg, gradually working in the flour so that a smooth dough is formed. Stir in the rest of the beer and cover the bowl. Let it rest for 30-60 minutes so that the flour can swell and the dough becomes thicker. Then, if necessary, dilute the dough with a little beer. Beat the egg white until stiff and fold in. Cut the fish fillets into bite-sized pieces, season with salt and pepper, cover with the batter and fry in plenty of hot oil or in the deep fryer at 190 ° C until golden yellow. Serve with aioli and salad.