Preheat your oven to 350°F (175°C). Roll out the shortcrust pastry and fit it into a tart pan. Press it firmly against the edges to prevent shrinking during baking.

Cover the pastry with parchment paper and add pie weights or dried beans on top to blind bake it. Bake for about 15 minutes.

Remove the parchment and weights, and bake for an additional 5 minutes or until the crust is lightly golden. Let it cool while you prepare the filling.

In a saucepan, heat the whole milk and heavy cream over medium heat until it is just simmering. Do not let it boil.

In a mixing bowl, whisk together the eggs, sugar, cornstarch, and vanilla extract until smooth.

Slowly pour the warm milk and cream mixture into the egg mixture, whisking constantly to temper the eggs. Stir in the melted dark chocolate until everything is well blended and homogenous.

Pour the chocolate custard into the prepared pastry shell, ensuring it is evenly distributed.

Bake the flan in the oven for 35–40 minutes. It should be set but slightly wobbly in the center when done.

Once baked, remove the flan from the oven and allow it to cool completely at room temperature. After cooling, refrigerate for at least 4 hours, but overnight is preferred for the best set.

Use a sharp knife to slice the flan for clean pieces. Optionally, garnish with whipped cream or fresh berries for an added touch of elegance.