For the Pumpkin Cake: Preheat the oven to 350 degrees F. Set out a 9 X 13 inch Pyrex Deep dish. In a medium mixing bowl, combine the flour, pumpkin pie spice, baking powder, baking soda, and salt. Whisk well.
In the bowl of an electric mixer, cream the butter and sugar together on high, until light and fluffy, about 3-5 minutes. Scrape the bowl with a rubber spatula. Then turn the mixer on low and beat in the eggs, followed by the pumpkin puree.
Slowly add the flour mixture to the wet mixture. Once fully combined, scrape the bowl of the mixer again. Beat for another 10 seconds, just until smooth. (Over-beating batter makes tough cakes.)
Pour the cake batter into the baking dish. Bake for 20-25 minutes, until the center is puffed, and a toothpick inserted into the center comes out clean. Cool completely before moving on.
For the Cheesecake Layers: Pour cold heavy cream into a clean stand mixer bowl. Using a whip attachment, beat on high until whipped into firm peaks. Scoop all the whipped cream into a separate bowl.
Then place the cream cheese, powdered sugar, and vanilla in the stand mixer. Beat on high until light and fluffy. Scrape the bowl with a spatula and beat again to make sure there are no clumps. Then place half of the whipped cream into the mixer and beat on low until the cream cheese and whipped cream create a smooth thick filling. Place the remaining whipped cream in the refrigerator for later use.
Spread the cheesecake filling over the cooled pumpkin cake. If it feels very loose, place in the refrigerator for 20+ minutes to firm up. Otherwise, proceed.
Sprinkle 3/4 cup chopped pecans over the cheesecake, reserving some for the top. Warm the dulce de leche in a microwave-safe bowl until just soft enough to spread easily. (NOT HOT!) Stir well, then pour and spread the caramel evenly over the top of the cheesecake layer.
Warm the fudge in the microwave until just warm enough to pour and spread. (Again, NOT HOT!) Pour the fudge over the caramel and quickly spread into an even layer.
Chill the cake just until the fudge is cool, about 10 minutes. Then spread the remaining whipped cream over the top of the cake. Sprinkle with the remaining pecans, and chocolate shavings if desired. Chill until ready to serve.
This can be made up to 3 days ahead. Cover and chill until ready to serve. Then set out at room temperature at least 30 minutes before serving.