You can make your own pumpkin spice for this recipe or use store-bought. You will need: ginger, cloves, allspice, cinnamon, and nutmeg. And by making your own you get to control the amount of each spice you add.
Place milk, some of the pumpkin spice, and pumpkin puree in a small saucepan. Bring it to a boil. Turn the heat off.
Slowly add the hot pumpkin/milk mixture to the egg/sugar mixture. Add one spoonful, whisk until incorporated, then add another spoonful. Do this until the whole mixture is incorporated.
Now, return this mixture to the saucepan, to cook the custard until thickened. Cook, stirring non-stop, for a few minutes, until it becomes thick. Then, transfer it to a bowl, cover it with plastic wrap, and refrigerate it until completely cool.
Once the Pumpkin Custard has completely cooled down, remove it from the fridge. Whisk it with the mascarpone cheese. Set it aside. This is going to be one of the layers of your Pumpkin Tiramisu.
When assembling the trifle, we will start with one layer of Ladyfingers dipped in coffee + Kahlua mixture.
Spread the remaining 1/3 of whipped cream on top of ladyfingers for the final layer. Place it in the fridge for at least 24 hours.