Step 1: Prepare the Shortcrust Pastry

• In a mixing bowl, rub the cold butter into the flour using your fingertips until it resembles fine breadcrumbs.
• Stir in the caster sugar and a pinch of salt.
• Add the egg yolk and cold water gradually, mixing until a dough forms.
• Shape into a ball, wrap in cling film, and chill for 30 minutes.

Step 2: Make the Blackcurrant Filling

• In a saucepan over low heat, combine the blackcurrants, caster sugar, lemon juice, and vanilla extract.
• Cook gently for 5-7 minutes until the fruit softens.
• Stir in the cornflour and cook for another 2 minutes until thickened.
• Remove from heat and let the mixture cool slightly.

Step 3: Roll Out the Pastry

• Preheat oven to 200°C (180°C fan) or 400°F.
• Roll out two-thirds of the pastry on a floured surface and line a 20cm pie dish.
• Trim any excess and prick the base with a fork.

Step 4: Blind Bake the Pastry

• Line the pastry with baking parchment and baking beans.
• Bake for 12 minutes, then remove the parchment and beans and bake for another 5 minutes until lightly golden.

Step 5: Fill and Assemble the Pie

• Pour the blackcurrant filling into the pre-baked pastry case.
• Roll out the remaining one-third of the pastry and lay it over the filling, sealing the edges.
• Cut small slits on top to allow steam to escape.

Step 6: Bake Until Golden

• Brush the pie with beaten egg and sprinkle with granulated sugar.
• Bake for 25-30 minutes until the pastry is golden brown.

Step 7: Cool and Serve

• Allow the pie to cool for at least 15 minutes before slicing.
• Serve warm or cold with custard, cream, or ice cream.