Process all crust ingredients, except maple syrup, into a crumble in a food processor. Add maple and process again to combine. Transfer this mixture into a 5" springform pan and press down into a crust.
Blend all filling ingredients, except for ¼ tsp of the spirulina powder (so only use the first ⅛ tsp at this stage), into a completely smooth consistency. Remove about ⅓ cup of this mixture and set aside. Add the remaining ⅛ tsp spirulina and blend once again to combine.
Pour the blended mixture over the cake crust. Spoon the lighter mixture on top bit by bit, and swirl it in gently. Decorate with starfruit and sprinkle with "sand" if desired. Freeze for 5-6 hours or overnight and enjoy! Keep leftovers frozen.
*See notes above recipe for details on whether to soak or not soak the cashews.
**I used this 5" pan to make this cake. To make a 6" cake, triple the ingredients.