Step 1. Prepare the Pastry Crust

In a mixing bowl, combine the plain flour and cold, cubed butter. Rub together with your fingertips until the mixture resembles breadcrumbs. Add the icing sugar and egg yolk, and mix well. Gradually add cold water, one tablespoon at a time, until the dough comes together.

Step 2. Chill and Roll Out the Dough

Shape the dough into a disc, wrap it in plastic wrap, and chill in the fridge for 20-30 minutes. After chilling, roll out the pastry on a lightly floured surface to about 1/4 inch thick. Line a 9-inch tart tin with the pastry, pressing it into the edges. Trim any excess pastry.

Step 3. Blind Bake the Pastry

Preheat your oven to 200°C (180°C fan) or 400°F. Line the pastry with parchment paper and fill with baking beans or rice. Blind bake for 10 minutes, then remove the parchment and beans and bake for an additional 5 minutes until lightly golden. Set aside to cool.

Step 4. Make the Chocolate Filling

In a saucepan, heat the milk and double cream over medium heat until it begins to steam (do not boil). In a separate bowl, whisk the egg yolks, caster sugar, and vanilla extract together until smooth. Slowly pour the hot milk mixture into the egg mixture, whisking constantly to avoid curdling.

Step 5. Melt the Chocolate and Combine

Place the chopped dark chocolate in a heatproof bowl. Pour the hot custard mixture over the chocolate, stirring until smooth and fully melted. Let it cool slightly before pouring it into the prepared pastry crust.

Step 6. Chill the Pie

Pour the chocolate filling into the baked crust and smooth the top. Place the pie in the fridge for at least 2 hours, or until the filling is set.

Step 7. Whip the Cream and Garnish

Before serving, whip the double cream until soft peaks form. Spread the whipped cream over the top of the chocolate pie, and garnish with shaved chocolate or a dusting of cocoa powder, if desired.