Line a 9x5x3-inch loaf pan with plastic wrap; set aside. For syrup, in a small bowl, combine maple syrup and bourbon. Set aside.
For filling, in a small bowl, combine pumpkin, cinnamon, ginger, and salt. In a small mixing bowl, combine 1/2 cup whipping cream and granulated sugar. Beat with an electric mixer on medium speed until soft peaks form (tips curl). Gently fold whipped cream into pumpkin mixture.
For topping, in another small mixing bowl, combine mascarpone cheese and powdered sugar. Beat on low speed until combined. Gradually beat in 1/2 cup whipping cream just until thickened (do not overbeat).
To assemble, arrange half of the ladyfingers in a single layer in the bottom of the prepared pan. Drizzle evenly with half of the syrup. Top with half of the filling, spreading evenly. Arrange remaining ladyfingers in a single layer over filling. Drizzle with remaining syrup and top with remaining filling. Dollop topping over filling. Using the back of a spoon, carefully spread topping evenly over filling. Cover and chill for 8 to 24 hours.
Use the plastic wrap to lift tiramisu out of pan. Place tiramisu on a serving platter. Sprinkle with nutmeg. Carefully cut the dessert crosswise into slices. Makes 6 servings.