Whisk the Cream: In a large mixing bowl, combine 300ml double cream and 75g icing sugar. Using an electric whisk or manual whisk, beat the mixture until soft peaks form, about 3-5 minutes.
Combine with Mascarpone: Gently fold in 250g mascarpone and 100g pistachio paste to the whipped cream mixture, being careful not to deflate the cream too much. Mix until everything is well blended and creamy.
Prepare the Sponge Fingers: In a shallow dish, pour 100ml strong coffee. Quickly dip 200g savoiardi sponge fingers into the coffee for a few seconds on each side, ensuring they soak but don't become soggy.
Layer the Ingredients: Start by layering soaked sponge fingers at the bottom of your serving dish. Spread a generous layer of the pistachio cream (from step 2) over the sponge layer.
Repeat Layers: Continue layering by adding another layer of coffee-soaked sponge fingers and then topping again with pistachio cream. Repeat this process until you've used all ingredients, finishing with a layer of pistachio cream on top.
Add Decoration: Using a piping bag, pipe additional pistachio paste on top of the dessert, creating a decorative pattern. Use a toothpick to create feathered designs if desired.
Chill: Cover the dish with plastic wrap and chill in the refrigerator for a minimum of 6 hours, ideally overnight. This allows the flavors to meld together and the dessert to set.
Serve: About 20 minutes before serving, remove the tiramisu from the fridge. Top with chopped pistachios for added crunch and presentation. Enjoy!