Cooking oil spray, to grease
3 sheets store-bought frozen shortcrust pastry
1 free-range egg white
5 free-range egg yolks
1 free-range egg
2 Tbsp custard powder
1 tsp vanilla extract
500ml thickened cream
125g caster sugar
1 whole nutmeg
Preheat oven to 200°C fan- forced (220°C conventional). Lightly grease 8 x 10cm round foil pastry cases with cooking oil spray. Cut pastry sheets to fit tart shells. They will shrink a little, so allow them to overhang slightly. Line pastry cases with baking paper and fill with baking weights or dried beans to blind bake.
Bake for 15 minutes and reduce heat to 140°C fan-forced (160°C conventional). Remove tarts from oven and remove baking paper and weights. Brush inside of cases with egg white and cook for a further 5 minutes. Remove from oven and carefully trim off excess pastry using a small sharp knife. Set aside to cool.
Put yolks, egg, custard powder and vanilla in a large bowl and whisk until smooth. Put cream, milk and sugar in a medium saucepan over medium heat. Heat, stirring, until just about to simmer. Then pour hot milk mixture into egg mixture, whisking constantly as you pour.
Strain mixture through a fine sieve, over a large jug. Put tart shells on 2 large oven trays, then pour custard mixture evenly into pastry cases. Bake for 25 minutes, then check if the custard has set. Cook a little longer if necessary.
Remove from oven and grate fresh nutmeg over the top. Allow tarts to cool before serving.