Step 1
Sift the flour and salt into a large mixing bowl. Use your fingertips to rub the Trex into the flour until the mixture looks like fine crumbs. Stir in the caster sugar. Add 4-5 tbsp chilled water and mix it in with a knife until the pastry clings together. Form the dough into a ball, then wrap and chill for 10 minutes.
Step 2
Preheat the oven to 200°C/fan oven 180°C/Gas Mark 6.
Step 3
Roll out about two-thirds of the pastry on a lightly floured surface and use it to line a 23cm (9in) diameter deep pie dish. Roll out the rest of the pastry to form the lid, then set it to one side.
Step 4
Put the cherries into a large bowl and add the caster sugar and cornflour, tossing to mix. Tip into the pie dish and sprinkle 4 tbsp cold water on top. Dampen the edges of the pastry, lift the lid on top and press the edges together to seal. Trim with a sharp knife. Re-roll the trimmings and use them to make pastry leaves.
Step 5
Brush the surface of the pie with the glaze, decorate with pastry leaves and brush them with the glaze. Sprinkle with caster sugar and bake for 30-35 minutes, until golden brown. Serve with fresh cream, ice cream or custard.