Soak the cashews overnight or do a quick soak method by bringing them to a boil in a small sauce pot with water just to cover, turn off heat & let stand for 30 minutes to soften, then drain
Prepare half recipe of the gingerbread cake recipe as per the instructions on that post & bake it in a greased & parchment lined 8" cake pan
Next prepare the ganache recipe & let it cool to room temperature
Set up your 8" springform pan without the bottom or a cake ring mold with acetate cake strip & place it on a sheet pan or cake board
Place the cooled gingerbread cake into the bottom of the mold
Make the pumpkin mousse by heating it over low heat with the agar powder & bring it to a boil. Boil just for about 30 seconds to activate the agar, then cool to tepid (not cold or the agar will thicken before we can whip it)
Combine the soaked cashews, pumpkin, confectioner's sugar & coconut milk in a high speed blender or food processor & blend smooth on high for about 30 seconds
Slowly pour the melted cocoa butter or white chocolate through the feed tube & continue processing for another 15 seconds. Transfer to a large mixing bowl
Whip the warm aquafaba with a balloon whip attachment to stiff glossy peaks then fold into the pumpkin mixture
Pour into the prepared mold on top of the gingerbread cake and refrigerate until set at least 5 hours or overnight.
Unmold the cake & then ice the cold set pumpkin mousse cake with cool but still pour able ganache
Garnish with pecans & optional pumpkin buttercream