Preheat the oven oven to 350°F/175°C.
Make the crust: Finely crush the black sesame seeds using an electric spice grinder, coffee grinder, or mortar and pestle.
In a food processor, pulse the walnuts until they are finely ground. Add the ground black sesame seeds, maple syrup, salt, ginger, and cocoa powder and blend until well combined and the dough sticks together when pressed between your fingers.
Press the dough evenly on the bottom and up the sides of a 9-inch or 10-inch tart pan. Place the pan in the freezer to set while you make the filling.
Make the filling: Drain the soaked cashews and give them a rinse. Add the cashews to a high-powered blender or food processor and blend them until they start to break down and blend together. Then add all of the remaining filling ingredients including the homemade pumpkin pie spice, and blend until the filling is very smooth and creamy, scraping down the sides as needed.
Pour the filling on top of the chilled crust and smooth out with a silicone spatula. Tap the pan against the counter a few times to release any air bubbles.
Bake the tart in the preheated oven for 45-50 minutes until the filling is set and no longer jiggly or loose. Allow the tart come to room temperature. Then refrigerate for at least 2 hours before serving.
When ready to serve, if desired, serve each piece of the tart with a dollop of coconut whipped cream or frozen whipped topping and a sprinkle of black sesame seeds.