Roll half of pastry to 0 cm thickness on a lightly floured surface. Place in a 23 cm pieplate; set aside. Combine cider and sugar in a large saucepan; bring to a boil. Add apples; cook, uncovered, 8 minutes or until apples are tender. Drain, reserving syrup. Add enough water to syrup to measure 1- one third cups liquid; return syrup mixture and apples to saucepan. Combine cornstarch and 2 tablespoons water, stirring well; add to apple mixture. Stir in cinnamon; cook, stirring constantly, until thickened. Stir in butter. Spoon mixture into prepared pastry shell. Roll remaining pastry to 0 cm thickness; transfer to top of pie. Trim off excess pastry along edges. Fold edges under and flute. Cut slits in top of crust for steam to escape. Cover edges of pastry with strips of aluminum foil to prevent excessive browning. Bake at 190ºC or 45 to 50 minutes. Serve warm or ----