To make a base, line a 8x8 inch form with foil, extending up and over the sides by about one inch.
Place dates, pecans and salt in a food processor and blend on high until relatively finely ground. Press mixture into the base of your baking form evenly.
To make the filling, place all filling ingredients into a blender and blend on high until smooth (If you don't have a high speed blender, you might need to stop a few times and scrape down the sides to assist blending). Pour this mixture over the base and place into the freezer while you making the top layer.
Place pumpkin puree, and the rest of the top layer ingredients in a blender and process until smooth. Pour your pumpkin filling over the two previous layers. Smooth off with a spoon and place into the fridge for a few hours (2-3 at least) or overnight, until set firm.
Defrost for 20-30 minutes before eating. Decorate your cake as you wish. Slice and serve!
I would recommend to slice all cake at once and store in the freezer in covered container for up to 1 month.