In a large mixing bowl, whisk the double cream and icing sugar until soft peaks form.

Gently mix in the mascarpone and pistachio paste until just combined.

Pour the coffee into a shallow dish. Quickly dip the savoiardi sponge fingers into the coffee, allowing them to absorb the flavor without becoming too soggy.

Arrange a layer of coffee-soaked sponge fingers at the base of a serving dish.

Spread a portion of the pistachio-cream mixture evenly over the sponge layer.

Repeat the process, layering sponge fingers and pistachio cream, ensuring the top layer is the pistachio cream.

Decorate by piping extra pistachio paste on top and using a toothpick to create a feathered effect.

Cover and refrigerate for at least 6 hours, preferably overnight.

Before serving, let it sit at room temperature for 20 minutes and garnish with chopped pistachios.