Line the base of a 23cm (9-inch) springform pan with parchment paper.
Place the digestive biscuits and pistachios into a food processor and pulse until fine crumbs form.
Add the melted butter and mix until the crumbs resemble wet sand.
Press the mixture firmly into the base and slightly up the sides of the prepared pan. Refrigerate for 30 minutes until firm.
In a large mixing bowl, beat the cream cheese, pistachio cream, and sifted icing sugar until completely smooth.
Add the double cream and continue beating for 2–3 minutes until the filling becomes very thick and holds its shape.
Spoon the filling onto the chilled crust and smooth the top with a spatula.
Refrigerate for at least 6 hours, preferably overnight, until fully set.
Carefully remove the cheesecake from the pan and transfer to a serving plate.
Warm the pistachio cream for about 20 seconds until pourable, then drizzle or spread it over the cheesecake.
Finish with chopped pistachios and serve chilled.