Begin by crushing about 24 gingersnap cookies until fine, using a food processor or a zip-top bag and rolling pin. In a bowl, mix the crumbs with 6 tablespoons of melted unsalted butter and a pinch of kosher salt. Press this mixture firmly into a 9-inch pie plate to create a nice even layer. Chill the crust in the refrigerator for at least 30 minutes to set.

In a large mixing bowl, blend 8 ounces of room temperature cream cheese and 1 cup of powdered sugar together until smooth and creamy, about 2-3 minutes with an electric mixer. Gradually mix in 1 cup of pure pumpkin puree, 1 teaspoon of vanilla extract, and 1 teaspoon of pumpkin pie spice, ensuring everything is well combined and there are no lumps in the pumpkin mousse filling.

In a separate chilled bowl, pour 1 cup of heavy whipping cream. Using an electric mixer, whip the cream on high speed until stiff peaks form, about 3-5 minutes. Be careful not to over-whip. Once done, gently fold the whipped cream into the pumpkin mixture in two batches, combining until smooth and airy.

Once the mousse is ready, carefully pour it into the chilled gingersnap crust. Use a spatula to gently smooth the top. Cover the pie with plastic wrap and place it back in the refrigerator. Chill for at least 3 hours, or ideally overnight, to allow the mousse to set properly into a creamy delight.

When you're ready to serve the Pumpkin Mousse Pie, create the whipped cream topping. In a chilled bowl, combine 1 cup of heavy whipping cream, 2 tablespoons of powdered sugar, 1 tablespoon of maple syrup, and a sprinkle of ground cinnamon. Whip on high speed until soft-stiff peaks form, which should take about 3-4 minutes.

After the mousse has set beautifully, take the pie out of the refrigerator. Spread the whipped cream topping evenly over the mousse. Garnish as desired, then slice and serve this delightful Pumpkin Mousse Pie to your eager guests!