Combine in a double boiler 1/2 cup quick tapioca and 1 pint of milk and stir over heat until tapioca is clear. Beat in 1 egg yolk, 1/8 teaspoon salt, 1 teaspoon vanilla extract and 1 cup sugar. Stir until thickened. Remove from heat. Fold in stiffly beaten egg white and chill. Brown the top under a broiler just before serving.