Using a hand mixer, beat the heavy whipping cream on high speed until stiff peaks form and the whipped cream is light and fluffy. (Refrigerate the whipped cream while you prepare the pumpkin cream.)
1/2 cup heavy whipping cream, whipped
In a separate bowl, beat the mascarpone cheese until smooth and creamy. Add the pumpkin puree, powdered sugar, pumpkin pie spice, and vanilla extract, and mix until well combined.
8 oz mascarpone cream, 1/2 cup pumpkin puree, 1/2 cup powdered sugar, 1 tsp pumpkin spice seasoning, ½ tsp vanilla extract
Gently fold the whipped cream into the pumpkin mixture using a spatula. Continue folding until the mixture is smooth and fully combined. (Do not overmix.)
In a separate bowl, combine the boiling water and instant coffee. Stir until the coffee is completely dissolved, then set aside to cool slightly.
1/4 cup instant coffee, 1 cup boiling water
In a small casserole dish or serving platter, spread a thin layer of the pumpkin cream over the bottom of the dish. (I use a 7.5 x 6-inch casserole dish.)
7 oz lady fingers
Quickly dip each ladyfinger into the cooled coffee, turning it briefly to coat all sides. (Remove it immediately so the ladyfingers don't become too soggy.)
Arrange the soaked ladyfingers in a single layer, covering the bottom of the dish.
Spread a layer of the pumpkin cream over the ladyfingers, reserving some of the cream for the final layer.
Repeat with another layer of coffee-soaked ladyfingers, followed by the remaining pumpkin cream.
Sprinkle the top with a mixture of cocoa powder, cinnamon and pumpkin pie spice.
Cover the dish and refrigerate for at least 4 hours, or preferably overnight, to allow the tiramisu to set and the flavors to come together.
Scoop and serve chilled.