• In a food processor, combine pumpkin puree, cream cheese, light brown sugar, cinnamon, pumpkin pie spice, and nutmeg; process until smooth and thoroughly combined.
• With machine running, add maple syrup, and continue to process until combined. Set aside.
• In your mixer's bowl, beat 1 cup heavy cream on high until stiff peaks form, 2 to 3 minutes.
• Using a rubber spatula, gently fold previously prepared pumpkin mixture into whipped cream.
• Refrigerate until ready to use, or at least 30 minutes.

In the meantime, prepare the Whipped Cream.

• In your mixer's bowl combine heavy cream, vanilla, and sugar.
• Beat mixture until stiff peaks form.
• Refrigerate until ready to use.

Assemble

• Spread a little whipped cream on the bottom of a long and narrow plate or in a 9x13 pan.
• Place one single layer of 4 whole graham crackers over whipped cream.
• Spread 1/3 of the vanilla whipped cream over graham crackers.
• Spread 1/3 of the pumpkin mousse over whipped cream.
• Place a single layer of 4 whole graham crackers over pumpkin mousse.
• Continue to layer until you've used up all ingredients, ending with whipped cream to cover the entire cake.
• Cover the pan with plastic wrap and place in the freezer for at least 6 hours or overnight.
• Top with chocolate shavings and chopped pecans.
• Cut and Serve.