To prepare the crust, line a springform pan with parchment paper and combine all of the ingredients in a medium mixing bowl creating a shortbread-like dough. Press the dough into the bottom of the pan evenly, creating a thin crust, and set it aside.
To prepare the pumpkin filling, grind the cashews in a blender or food processor until they are very finely ground (it's okay if they start to turn into cashew butter). Add in the rest of the filling ingredients and blend until smooth, stopping to scrape down the sides of the container if necessary. If you're using cashew butter, you can skip the blender and just mix all of the filling ingredients together in a bowl until very smooth. Pour the filling over the crust and use a spatula to spread the filling to the edges and smooth the top. Set aside.
To prepare the chocolate topping, combine the three ingredients in a small bowl and stir well to combine. Transfer the chocolate to an icing bag or to a plastic sandwich bag with the tip cut off. Pipe the chocolate topping in a spiral design, starting from the center and working your way towards the edge of the cheesecake. Drag a knife from the center of the spiral to the edge of the pan, almost like you're slicing it into pieces to create a spider web-like design. (Even with my splotchy icing skills, I think the result still looks pretty impressive, so it's hard to mess this up!)
Place the pan in the freezer to set until firm, about 4 to 6 hours or overnight. Once firm, you can transfer the cheesecake to the fridge for a softer more cheesecake-like texture, but keep in mind that this cake will start to melt at room temperature, so serve it quickly after slicing. (You can serve it directly from the freezer, too, but the flavors aren't as strong when frozen-- it gets better after sitting on the counter for about 10 minutes.) I'd recommend storing any leftovers in the fridge for up to a week, but if you want to store it longer it should keep indefinitely in the freezer when stored in an airtight container.