1. Place banana in plastic bag; freeze for 4 hours, or until completely frozen.
2. Place cashews in a medium bowl. Cover with water. Let stand for 30 minutes; drain.
3. Place drained cashews, frozen banana, and raspberries in blender; cover. Blend until smooth. Add water, 2 Tbsp. at a time, if needed for consistency.
4. Pour into a freezer-safe container; freeze until set.