Line the mould with puff pastry

• Butter the springform pan.
• Roll out the puff pastry and line the pan, pressing it well into the edges and letting it overhang slightly.
• Chill the lined pan while preparing the filling.

Make the pistachio custard

• Warm the milk and cream in a saucepan with the pistachio paste and vanilla.
• Whisk the egg yolks with the sugar and cornstarch in a bowl until pale.
• Pour the warm milk over the yolks while whisking, then return everything to the pan.

Thicken the custard

• Cook over medium heat, whisking constantly, until the cream thickens.
• Remove from the heat and let it cool slightly.

Fill and bake

• Pour the pistachio custard into the pastry-lined pan and smooth the top.
• Bake until the pastry is golden and crisp and the filling is set.

Cool and finish

• Let the flan cool completely in the pan, then unmould onto a cooling rack.
• Scatter the chopped pistachios over the top before serving.