Preheat oven to 190ºC. Combine flours and 1¼ cup of the sugar in a bowl. Rub in butter until mixture resembles fine breadcrumbs. Add 1 egg and enough water (about 3 tsp) to make ingredients cling together. Press into a ball then shape into a disc and wrap in plastic wrap. Place in fridge for 30 minutes to rest.
On a lightly floured surface, roll dough into a circle about 30cm in diameter. Lift pastry into springform tin. Cover with cling wrap and place in fridge for 30 minutes to rest.
Place tin on oven tray, cover pastry with baking paper and fill with uncooked rice or baking beads. Bake for 10 minutes then remove paper and weights and bake for 10 more minutes until pastry is golden. Set aside for 30 minutes to cool. Reduce oven temperature to 180ºC.
Meanwhile, whisk together remaining eggs, vanilla extract and remaining sugar in a bowl. Slowly add hot milk and whisk until combined.
Pour custard into pastry. Bake for 15 minutes. Sprinkle with nutmeg and bake for a further 30 minutes or until custard is set. Set aside for 15 minutes to cool. Place in fridge to chill for 30 minutes before serving.