In a medium bowl, stir together hot coffee, sugar, bourbon, and vanilla extract until the sugar is dissolved. Set aside.
Set a medium pot with two inches of water over medium heat to simmer. In a heatproof bowl whisk together egg yolks, sugar, and Marsala. Place the bowl over the simmering water. Using a whisk or a hand beater, beat the egg mixture until it is pale and tripled in volume, about 8 minutes. Remove from the heat.
In a medium bowl whisk together mascarpone, pumpkin, all of the spices, and sea salt. Add the pumpkin mixture to the eggs and stir until just combined.
Beat the cream, powdered sugar, and vanilla in a large bowl until it forms stiff peaks. Divide the whipped cream in half, reserving half of the whipped cream to top the tiramisu.
Fold the mascarpone mixture into the whipped cream, keeping the mixture as fluffy and aerated as possible.
To assemble the tiramisu, dip both sides of a lady finger into the coffee mixture. Arrange in the in the bottom of a 9×13-inch pan – 3 rows, 18 fingers total. Trim any edges, to fit.
Spread half of the mascarpone filling on top of the dipped lady fingers. Add another 18 dipped lady fingers on top of the first layer and finish with the remaining mascarpone mixture. Layer with the remaining whipped cream and dust generously with cocoa powder. Refrigerate for at least 6 hours or overnight.
Let the tiramisu rest at room temperature for 30 minutes before slicing. Dust with more cocoa if desired. Enjoy!