1.Stir the water and sugar in medium saucepan over low heat until sugar has dissolved. Add quince and rind; bring to the boil. Reduce heat, then simmer with the lid on for about 2 hours, or until quinces are tender and a rosy colour. Add rhubarb and cook 5 minutes or until rhubarb softens. Add juice to taste, to reduce sweetness. Cool quince and rhubarb in the syrup.
2.Meanwhile, process flour, icing sugar and butter until crumbly. Add egg yolk and iced water, process until ingredients just come together. Knead gently on a floured surface until smooth. Cover and refrigerate for 30 minutes.
3.Preheat oven to 180°C (160°C fan-forced). Grease 23cm pie dish.
4.Drain fruit mixture, reserving 1/3 cup of the syrup. Spoon fruit mixture and reserved syrup into dish.
5.Roll out pastry until large enough to cover pie. Using a 1cm cutter, cut out rounds from pastry, reserving rounds. Place pastry over filling, trim edge with a knife. Place rounds on pastry, brush a little of the lightly beaten egg white over pastry; sprinkle with raw sugar. Place pie on an oven tray.
6.Bake for about 30 minutes or until well browned. (Cover the edges of the pastry with foil after 20 minutes to prevent over-browning.) Stand 10 minutes before serving with thickened cream.