Use an electric hand mixer or whisk to whip the pumpkin puree, brown sugar, cinnamon, ginger, and nutmeg together in a medium bowl. Then add the mascarpone cheese and whip the mixture until it’s thoroughly combined.
Pour the heavy cream into the bowl. Now, whip the cream into the pumpkin mixture until it’s light and fluffy.
Stir the warm coffee and sugar together in a shallow bowl until the sugar is fully dissolved.
Dunk half of the ladyfingers one at a time into the coffee mixture and then place each one in a single layer on the bottom of a 9x13-inch baking dish. You need to moisten both sides of the cookies without making them soggy. You may need to break some of them in half to cover the whole dish.
Spread half of the pumpkin mixture over the ladyfingers in an even layer.
Repeat the dunking process with the remaining ladyfingers and creamy pumpkin mixture to create a second layer.
Cover the baking dish and refrigerate the tiramisu for at least 8 hours or overnight.
To serve, sprinkle the top of the tiramisu with cinnamon. Then slice it into squares and enjoy.