In a shallow dish, whisk the warm espresso with 1 tablespoon of the pistachio butter and 2 tablespoons sugar until combined. Set aside and allow the mixture to cool to room temperature.

In a large bowl, beat the mascarpone with the remaining pistachio butter, sugar, and vanilla extract until smooth and creamy. In a separate bowl, whip the cold heavy cream to stiff peaks, then gently fold it into the mascarpone mixture until fully combined and fluffy.

Stir the espresso mixture and then briefly dip each ladyfinger into it and arrange in a single layer in the bottom of a 8-inch square dish. Add half of the pistachio mascarpone cream and use a small offset spatula to smooth evenly over the top. Repeat with a second layer of dipped ladyfingers and the remaining cream.

Cover and refrigerate for at least 6 hours or overnight. Before serving, top with chopped pistachios.