1. Shake the can of coconut milk to make sure it is emulsified and the milk is smooth, without any lumps. Open the can and pour half of the milk into ice cube trays. Freeze until solid. (Refrigerate the remaining coconut milk in an airtight glass container for another use.)
2. Peel bananas and cut crosswise into one-inch (two- and- a- half- centimeter) -thick slices. Arrange in a single layer on a baking sheet lined with waxed paper and freeze until solid.
3. Add coconut milk cubes and frozen banana slices to a blender and process to the consistency of soft-serve ice cream, stopping the blender to stir as needed for even blending. Serve immediately.