Cut pound cake into 16 about 1/2-inch-thick slices. Arrange half of the slices in the bottom of a 2-quart square baking dish. Brush cake slices with 1 tablespoon of the Frangelico. Set aside.
In a large bowl, beat whipping cream and 2 tablespoons powdered sugar with an electric mixer on medium speed until soft peaks form (tips curl). Set aside.
In another large bowl, combine mascarpone cheese, pumpkin, 3/4 cup powdered sugar, the 1 teaspoon cinnamon, the orange extract, the ground ginger, and the mace. Beat on medium speed until combined. Fold in half of the whipped cream.
Spread half of the pumpkin mixture over cake layer in dish. Top with the remaining cake slices; brush cake slices with the remaining Frangelico. Spread the remaining pumpkin mixture and the remaining whipped cream over layers in dish (dish will be very full). Cover and chill for 4 to 24 hours.
Before serving, sprinkle top with grated nutmeg.