In a mixing bowl, whip the heavy cream until stiff peaks form. Set aside.
In another bowl, combine the mascarpone cheese, pumpkin puree, sugar, and pumpkin pie spice. Mix until smooth.
Gently fold the whipped cream into the pumpkin mixture until well combined.
In a shallow dish, combine the brewed espresso and coffee liqueur (if using).
Dip each ladyfinger into the espresso mixture for a few seconds, ensuring they are soaked but not soggy.
Arrange a layer of soaked ladyfingers in the bottom of a 9x9 inch baking dish.
Spread half of the pumpkin mixture over the ladyfingers.
Repeat with another layer of soaked ladyfingers and the remaining pumpkin mixture.
Cover and refrigerate for at least 4 hours, or overnight.
Before serving, dust the top with cocoa powder.