1.Sift flour and icing sugar into a large bowl; rub in butter. Stir in egg yolk and enough of the water to make ingredients just cling together. Knead gently on floured surface until smooth. Cover, refrigerate 30 minutes.
2.Place milk in a large saucepan; bring to the boil. Meanwhile, whisk egg yolks, sugar and cornflour in a large heatproof bowl; gradually whisk in hot milk mixture. Return mixture to the pan; whisk over medium heat until mixture boils and thickens. Remove from heat; stir in extract. Cover surface of custard with plastic wrap; cool. Refrigerate until cold.
3.Preheat oven to 200°C/400°F. Grease six 10cm (4-inch) loose-based flan tins.
4.Divide pastry into 6 equal portions. Roll portions between sheets of baking paper until large enough to line tins. Lift pastry into pan; press over base and side, trim excess pastry. Prick base all over with a fork. Place tins on oven tray; refrigerate 20 minutes.
5.Bake about 15 minutes. Cool 5 minutes, remove cases from tins.
6.Peel and thinly slice bananas on the diagonal.
7.Divide custard among pastry cases. Arrange banana slices on top of flans. Drizzle passionfruit over banana slices. Refrigerate until ready to serve.
Unfilled pastry case can be made up to 3 days ahead; store in an airtight container. The creamy custard filling can be made a day ahead; store, covered, in the refrigerator.Note