Soak the cashews overnight or for at least 10 hours in a bowl big enough to completely submerge them. When you're ready to make the cheesecake, drain and rinse them before proceeding with the recipe.
Add the walnuts, dates, vanilla and sea salt to a food procecesor and blend into a crumbly be sticky dough you can easily pinch together between your fingers.
Line the bottom of a 8-9 inch springform pan with parchment paper (lining optional) then firmly press the dough into the bottom of the pan and about 1-1.5 inches up the sides. Use your fingers to smooth the edges. Place in the fridge while you make the filling.
Add all of the filling ingredients to a high-speed blender and start blending on low. Use a tamper if needed to keep things moving. As it starts to blend, slowly increase the speed and blend until it's completely smooth and very creamy. It should be almost mousse-like. The filling is quite pale so if you'd like it to come out more orange like pumpkin, you can add 1/4 tsp turmeric to add colour.
Pour the filling mixture over the prepared crust. Smooth the top the best you can using the back of a spoon or spatula.
Place the whole pan in the freezer for at least 2 hours to firm.
Remove from the freezer and let sit at room temperature for 20-30 minutes. Slice and serve immediately, with whipped cream and chopped pecans, if desired.