Step 1: Prepare the Pistachio Cream: In a food processor, pulse the shelled pistachios and granulated sugar until finely ground, resembling a powder.
Step 2: Mix with Cream: In a large mixing bowl, beat the heavy cream until soft peaks form. Gently fold in the mascarpone cheese, vanilla extract, and the ground pistachio mixture until fully combined and smooth.
Step 3: Prepare the Coffee Mixture: In a shallow dish, combine the cooled brewed coffee and coffee liqueur (if using). Stir to mix well.
Step 4: Dip Ladyfingers: Quickly dip each ladyfinger into the coffee mixture, ensuring they are soaked but not soggy.
Step 5: Layer the Dessert: Arrange a layer of dipped ladyfingers in the bottom of a 9×9-inch dish. Spread half of the pistachio cream over the ladyfingers, smoothing it out evenly.
Step 6: Repeat Layers: Add another layer of dipped ladyfingers on top of the pistachio cream, followed by the remaining pistachio cream. Smooth the top with a spatula.
Step 7: Refrigerate: Cover the dish with plastic wrap and refrigerate for at least 4 hours, or overnight for the best flavor and texture.
Step 8: Garnish and Enjoy: Before serving, sprinkle crushed pistachios on top and dust with cocoa powder if desired. Cut into squares and serve chilled.