Prepare the Pistachio Sponge Cake:
Preheat your oven to 350°F (175°C).
Line a 9x13-inch baking dish with parchment paper.
In a bowl, mix the flour, ground pistachios, baking powder, and salt.
In a separate bowl, beat the egg yolks with half of the sugar until fluffy.
In another bowl, beat the egg whites until soft peaks form. Gradually add the remaining sugar and beat until stiff peaks form.
Gently fold the egg yolk mixture into the egg whites. Then, sift in the dry ingredients and fold until combined.
Pour the batter into the prepared dish and bake for 20-25 minutes. Allow it to cool completely.
Prepare the Mascarpone Cream:
In a mixing bowl, whisk together mascarpone cheese, heavy cream, powdered sugar, and vanilla extract until smooth and thick.
Assemble the Tiramisu:
Mix the cooled espresso and non-alcoholic coffee syrup in a shallow dish.
Slice the pistachio sponge into layers and dip each layer into the coffee mixture.
In a trifle or serving dish, layer the dipped pistachio sponge, followed by a layer of mascarpone cream.
Repeat the layers, finishing with a final layer of mascarpone cream.
Dust the top with cocoa powder and sprinkle chopped pistachios for garnish.
Refrigerate for at least 4 hours, or overnight, for the best flavor.