Apple and custard pie

Method

1. To make the pastry, sift the flour, custard powder and a pinch of salt into a large bowl or food processor. Add the butter and rub together with your fingers (or whizz in a processor) until it resembles breadcrumbs. Add the beaten egg and just enough water to bring the dough together, then knead briefly. Shape into a disc, wrap in cling film, then chill in the fridge for 30 minutes.
2. Heat the milk and cream in a saucepan until almost boiling. Meanwhile, whisk the egg yolks, cornflour and caster sugar together in a bowl. Pour the hot milk over the egg yolks and whisk, then return to a clean pan over a low heat and cook, stirring, until it’s thick enough to coat the back of a spoon. Stir through the nutmeg and pour into a jug. Cover the surface with cling film to prevent a skin forming, then leave to cool completely.
3. Preheat a baking sheet in the oven to 180°C/fan160°C/gas 4. Mix the apples, lemon juice and demerara sugar together, then set aside. Roll out the pastry on a lightly floured surface to a rough 40cm circle, about 3mm thick. Line a shallow 20cm loose-bottomed cake tin with paper (so it hangs over the sides), then line with the pastry.
4. Pile the apples into the centre of the pie and bring the sides of the pastry up around the filling, crimping and pinching to seal. Pour the cold custard into the hole in the centre.
5. Brush the pastry with the beaten egg, then sprinkle with demerara sugar. Transfer immediately into the oven and bake for 50 minutes until the pastry is golden and the custard almost set. Remove from the oven and allow to cool for 20 minutes in the tin before carefully removing, using the paper. Serve the pie in generous wedges.