In a medium sized mixing bowl with a hand or stand mixer, beat together the mascarpone, pumpkin puree, sugar, vanilla bean paste, salt and pumpkin pie spice just until combined.
Slowly beat in the heavy whipping cream. Continue to beat until the mixture reaches stiff peaks.
Line a 9x5" loaf pan with parchment paper to form a hammock for the tiramisu so it's easier to pull out later on.
Quickly dip the ladyfingers into the espresso mixture on both sides, then layer them into a single layer on the bottom of the loaf pan
Top with ⅓ of the mascarpone cream mixture and smooth it out into an even layer.
Dip more of the ladyfingers into the espresso mixture, and layer them on top of the mascarpone
Spread ½ of the rest of the mascarpone cream on top of the ladyfingers. Then, top it off with another layer of espresso-soaked ladyfingers, followed by the remaining mascarpone cream.
Cover the tiramisu with plastic wrap, and set it in the fridge to chill and firm up for at least 4 hours. Once you're ready to serve the tiramisu, make the whipped cream.