Making Pistachio Tiramisu is a straightforward process if you follow these steps:

1. Prepare the Pistachio Cream: In a mixing bowl, combine the ground pistachios, mascarpone cheese, and granulated sugar. Whip until smooth.
2. Add Heavy Cream: In a separate bowl, whip the heavy cream until stiff peaks form. Gently fold the whipped cream into the pistachio mixture until well combined.
3. Mix Coffee and Liqueur: In a shallow dish, combine the cooled brewed coffee and coffee liqueur (if using).
4. Soak Ladyfingers: Quickly dip each ladyfinger into the coffee mixture, ensuring they are soaked but not soggy.
5. Layer the Dessert: In a serving dish, arrange a layer of soaked ladyfingers at the bottom. Spread half of the pistachio cream over the ladyfingers.
6. Repeat Layers: Add another layer of soaked ladyfingers, followed by the remaining pistachio cream. Smooth the top with a spatula.
7. Chill: Cover the dish with plastic wrap and refrigerate for at least 4 hours, or overnight for the best flavor.
8. Serve: Before serving, dust the top with cocoa powder and sprinkle extra crushed pistachios for garnish.

These simple steps will guide you in creating an unforgettable Pistachio Tiramisu that will wow your guests.