Step 1
Sift the flour and salt into a large mixing bowl and rub in the Trex with your fingertips until the mixture looks like fine crumbs. Add three to four tbsp chilled water and mix in with a round-bladed 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 the pastry on a lightly floured surface and use it to line six 10cm (4in) individual tartlet tins. Line each one with a piece of crumpled foil or baking paper and baking beans and bake ‘blind’ (i.e. without a filling) for 15-20 minutes.
Step 4
For the filling, put the egg yolks, sugar, vanilla, flour and milk into a saucepan. Heat slowly, whisking constantly, until the sauce is smooth and thick. Cool a little, stirring to prevent a skin from forming.
Step 5
Take the tarts from the oven and remove the foil or baking paper and beans. Share the sauce between them and leave until cold.
Step 6
Top each tart with fresh berries, then serve, sprinkled with a little icing sugar.