• Pour boiling water over cashews and let sit for at least 30 minutes.
• Preheat oven to 350

Make Crust

• Remove pits from dates and roughly chop. Add to bowl of food processor with the walnuts, cinnamon and salt. Process until thoroughly combined. It will resemble a mixture between a crumbly mixture and a rough paste, and definitely will hold together when pressed between 2 fingers.
• Pour walnut and date mixture into a tart pan with removable bottom. It may look like there's too much, but it will flatten and be the perfect amount of crust for this tart.
• Press walnut mixture evenly into the bottom and up the sides of the tart pan. I use barely damp hands for this, and then use the bottom of a glass or dry measuring cup to be sure it's flat against the bottom surface of the pan. Set aside.

Make the Custard Filling

• Drain cashews, rinse with clean water and then drain again. Add drained cashews into a blender. Use the food processor if you don't have a blender, but the custard cream will be a bit smoother if you use a blender.
• To the blender with the cashews, add the water, maple syrup, and cinnamon. Blend until smooth and creamy.

Assemble and bake the tart

• Spoon ¾ of the custard mixture into the tart pan with the walnut crust. It will act as the glue that holds the apples in place!
• Slice apple super thin and arrange in a circle starting with the outside of the tart, working round and round until the pan is full and the apple slices are all used up. Drag a bit of the custard along with you as you place the apples, so it's in between the apple slices too.
• Thin the remaining custard by using a fork or whisk to incorporate 1 tablespoon water. Then drizzle it onto the top and into the crevices between apple slices. Sprinkle the top with cinnamon if desired.
• Bake in preheated 350 oven for 25-30 minutes. Timing will depend on how thin you were able to slice the apples. You want them to be tender, but not completely falling apart.
• Allow tart and custard to cool before removing the outer layer of the tart pan and transferring to serving plate.
• Cool completely before covering and storing in the fridge.
• Slice into pieces. Walnut tart with apple custard filling can be served cold or at room temperature.
• Store covered in the fridge for 3-4 days.