Form pie shell by pressing 12"-square heavy-duty aluminum foil in 9" pie pan. Cut off excess at rim. Carefully remove foil pie shell. Sprinkle in chocolate pieces and place on baking sheet in very slow oven (250°F.) for 5 minutes. Remove and set aluminum shell in pie pan. Add shortening and blend with back of spoon. Add confectioners sugar; blend. Spread mixture evenly on bottom and sides of foil shell. Chill until well set.
Carefully remove foil and return chocolate liner to pie pan. Fill with chiffon-pie filling.