Prepare the pastry:Beat butter until creamy, add sugar, beat until just combined. Add lightly beaten egg gradually, beating well after each addition. Work in 2/3 sifted flours with wooden spoon, then remaining flour by hand. Turn onto a lightly floured board and knead lightly until smooth. Refrigerate 30 minutes before using. Roll pastry and line greased 20 cm pie dish.
Handle pastry carefully making sure there are no breaks, otherwise uncooked custard will seep through. Brush base and sides of pastry with lightly beaten egg white.
Bake in moderate oven (350F) for 50-55 minutes. After 15 minutes cooking, sprinkle with cinnamon and nutmeg.
Do not overcook: Pastry will firm as it cools.