Step 1: Prepare the Pumpkin Mixture

1. In a medium bowl, whisk together the pumpkin puree, brown sugar, cinnamon, nutmeg, and ginger until smooth. Set aside.

Step 2: Make the Mascarpone Filling

1. In a large mixing bowl, beat the mascarpone cheese, heavy whipping cream, and vanilla extract with an electric mixer until fluffy and soft peaks form.
2. Gently fold in the pumpkin mixture until fully combined.

Step 3: Prepare the Coffee Mixture

1. In a shallow dish, combine the cooled espresso and coffee liqueur (if using). Stir gently to mix.

Step 4: Assemble the Tiramisu

1. Quickly dip each ladyfinger into the coffee mixture, ensuring they absorb just enough liquid without becoming soggy.
2. Arrange a single layer of dipped ladyfingers in the bottom of a 9×9-inch dish or a trifle bowl.
3. Spread half of the pumpkin mascarpone filling evenly over the ladyfingers.
4. Add another layer of dipped ladyfingers on top, followed by the remaining mascarpone filling.

Step 5: Chill and Decorate

1. Cover the dish with plastic wrap and refrigerate for at least 4 hours or overnight for the best flavor.
2. Before serving, dust the top generously with cocoa powder using a fine sieve.

Step 6: Serve and Enjoy

1. Slice or scoop the tiramisu into servings.
2. Optionally, garnish with whipped cream, chocolate shavings, or a sprinkle of cinnamon.