Ingredients

Step by step

1. Heat the oven to 180 ̊C, fan 160 ̊C, gas 4. Cut off a quarter of the pastry block, and chill. Roll out the larger piece on a floured work surface and use to line a loose-bottomed 23cm tart tin. Leave a 1cm overhang of pastry when trimming. Line with baking paper, fill with baking beans and bake for 10 minutes. Remove the beans and paper, and bake for another 5-10 minutes until it looks pale golden and dry.
2. As soon as you remove the pastry case from the oven, brush a little of the egg white inside the case to seal – this stops any leaks and keeps the base crisp. Trim the pastry edges with a sharp knife and leave to cool. Meanwhile, roll out the remaining pastry to the thickness of a £1 coin, then cut into long strips. Arrange the strips on a floured baking sheet to make a lattice, with 4cm holes between each cross.
3. Mix together the whole egg, sugar (depending on how sweet the custard is) and custard, then pour into the pastry and scatter over the blueberries. Use the remaining egg white to brush the pastry crust. Slide the pastry lattice carefully on top of the pie, press to seal, and trim the sides. Brush the strips with egg yolk; sprinkle over the demerara.
   Tip

   The sugar content varies in custards, so try yours to see how sweet it is (before adding the egg). Add a little vanilla extract, too, if you like 
4. Bake for 35-40 minutes until the pastry is golden and the filling still has a slight wobble but is set. Leave to cool to room temperature before slicing. Sprinkle with icing sugar, if you’re serving to the very sweet-toothed!
   Tip

   Use a ready-made sweet pasty case for an even quicker pie, and a ready-rolled shortcrust sheet, cut into strips, for the lattice.