For the zabaione: Add egg yolks, sugar, and hazelnut liquor into a mixing bowl and cook over a double boiler on low heat, while constantly whisking, until the mixture reaches 150°F on a digital thermometer.
Allow to cool for 10 minutes, and transfer to a medium-sized mixing bowl.
For the pumpkin chantilly: Add Mascarpone cheese, pumpkin puree, heavy cream, vanilla bean paste, icing sugar, and pumpkin spice to a mixer.
Beat on medium speed until the mixture reaches stiff peaks.
Fold the chantilly into the cooked zabaione mixture so it’s nice and airy.
Dip ladyfingers in espresso, then place them in a 9 x 9 baking pan, evenly lined up.
Spread half of the pumpkin tiramisu mixture over the lady fingers, followed by another layer of coffee dipped lady fingers, and the remaining pumpkin tiramisu mixture.
Transfer to a refrigerator to chill overnight.
Dust the tiramisu with cocoa powder before slicing and serving.
