Soften gelatin in cold water. Scald milk, salt + 1/4 cup sugar. Separate eggs. Beat yolks. Pour a little hot milk over eggs then stir onto rest of hot mixture. Cook over hot water until slightly thickened. Add gelatin + stir. Beat egg white until stiff, gradually fold in sugar. Fold into custard. Add maple flavoring to custard. Fold in walnuts. Add to pie shell. Chill. Decorate with half a walnut on top of whipped cream.