Preheat the oven to 350 degrees. Grease two 6-inch round cake pans and line the bottoms with parchment paper.
In a medium bowl, whisk together the flour, baking powder, baking soda, cinnamon, nutmeg, and salt.
In a separate bowl, mix the pumpkin puree, granulated sugar, brown sugar, eggs, vegetable oil, and bourbon until smooth.
Add the dry ingredients to the wet ingredients and stir until just combined. Divide the batter evenly between the prepared pans.
Bake for 22 to 25 minutes, until a toothpick inserted in the center comes out clean. Let the layers cool in the pans for 10 minutes, then turn them out onto a wire rack to cool completely.
In a clean bowl, beat the mascarpone with the maple syrup and powdered sugar until smooth and spreadable.
Place one cooled cake layer on a plate. Spread half the frosting over the top. Add the second layer and spread the remaining frosting over the top and sides.