1. Lightly oil a 9-inch springform pan. Cut 4-5 strips of parchment paper into strips about 12" x 2" and lay them crisscross along the bottom of the pan.
2. In a stand mixer, beat the whipping cream and sugar together until stiff peaks form. Set aside.
3. Beat the mascarpone until smooth. Add pumpkin and pumpkin pie spice; mix well. Fold in two-thirds of the whipped cream mixture.
4. Mix coffee and pumpkin liqueur in a bowl.
5. Cut ladyfingers in half, dip each side in the coffee mixture, and line the sides and bottom of the pan.
6. Spoon half of the pumpkin filling over ladyfingers, add another layer of dipped ladyfingers, then top with the rest of the pumpkin mixture.
7. Spread the remaining whipped cream on top and sprinkle with crumbled ginger snaps. Cover and chill for 8 to 24 hours.
8. To unmold, unlock the clasp and use parchment strips to move the tiramisu to a serving platter. Remove parchment strips, slice, and serve.