Sift 1/2 cup flour and salt into mixing bowl; stir in butter and egg, using wooden spoon.
Add beer gradually; mix until batter is almost smooth.
Do not overmix.
Let batter rest at room temperature for about 1 hour.
Beat egg white until stiff; fold into batter gently, blending well.
Heat shortening in deep fat fryer to 375 degrees.
Dip oysters into remaining flour; shake off excess flour.
Dip into batter; let excess batter drain off.
Fry oysters, five or six at a time, for 3 to 4 minutes or until puffed and golden brown.
Drain on paper towel.