Peel, quarter and core the apples and cut in thick slices. Place half the apples in a 1½-pt pie-dish, add the sugar and flavouring and pile the remaining fruit on top. Line the edge of the pie-dish with pastry and cover the pie with pastry. Knock up the edges of the pastry with the back of a knife. Bake for 40 min., first in a fairly hot oven (400° F., Gas 6), reducing the heat to moderate (350° F., Gas 4) when the pastry is set. Dredge with castor sugar and serve hot or cold. If liked, the pastry may by brushed with egg white and sprinkled with sugar before cooking.