Brew espresso and let it cool to room temperature. Meanwhile, whisk pumpkin puree, sugars, cinnamon, nutmeg, vanilla, and a pinch of salt until smooth.
In a separate bowl, whip cold heavy cream to soft peaks. Gently fold in mascarpone until fully combined and fluffy.
Add the pumpkin mixture and stir carefully to maintain airiness. The cream should be silky and light.
Dip each ladyfinger briefly in espresso—avoid soaking them completely to prevent mushiness—and place into serving cups or small glasses.
Spoon a layer of pumpkin-mascarpone cream over the soaked ladyfingers, then repeat with another layer of coffee-dipped biscuits and cream.
Smooth the tops with a spatula and dust with cocoa powder for that signature tiramisu finish.
Cover and refrigerate for at least 4 hours, preferably overnight, so the layers set and flavors meld.