Set up a double boiler by filling a saucepan with 1-2 inches of water and bringing it to a boil. Place a heatproof bowl over the saucepan (without touching the water).

In the bowl, whisk together egg yolks and sugar. Place over simmering water and whisk until the sugar dissolves.

Gradually add half-and-half, whisking constantly for 7-10 minutes until the mixture thickens and becomes fluffy.

Remove from heat and stir in pumpkin puree, cinnamon, and nutmeg. Let the custard cool completely.

In a separate bowl, mix mascarpone cheese and vanilla extract until smooth.

In another bowl, whip heavy cream and powdered sugar until soft peaks form.

Once the pumpkin custard has cooled, gently fold it into the mascarpone mixture.

Finally, fold in the whipped cream until fully combined, creating a light and fluffy filling.

In a shallow dish, combine the cooled coffee and chocolate liqueur.

Quickly dip each ladyfinger into the coffee mixture (about 1-2 seconds), then arrange them in a single layer in a 9x13-inch baking dish.

Spread half of the pumpkin mascarpone filling over the ladyfingers. Repeat with another layer of dipped ladyfingers and the remaining filling.

Cover the tiramisu with plastic wrap and refrigerate for 4-6 hours, or overnight for best results.

Before serving, dust the top of the tiramisu with unsweetened cocoa powder. Optional: garnish with shaved chocolate, whipped cream, or a drizzle of caramel.