Arrange dollops (about 3 tablespoons) of the puréed pumpkin and banana slices on a baking sheet lined with parchment paper or silicone liner in a single layer. Freeze until solid, about 4 hours.
Place cashews, maple syrup, vanilla, 1 cup water, and salt in a food processor or high power blender. Blend until smooth.
Add the frozen pumpkin, banana, and spices to the processor or blender. Blend until combined, about 2 minutes. Scrape down sides and use blender tamper to help distribute ingredients until smooth.
Enjoy as soft ice cream or transfer to a container with a lid and freeze. Remove 10 minutes before serving if frozen.
Notes
Tip: add 1 tablespoon of vodka to prevent the nice cream from freezing too hard.