Peel the bananas and slice into 1-inch chunks. Place in a single layer on a parchment-lined baking sheet (freezing in a single layer makes the slices easier to work with later). Freeze for 4–6 hours, or overnight.

Remove bananas from freezer, place in a food processor or high-powered blender and blend until smooth, pausing to scrape down the sides of the food processor/blender as you go. If necessary, use a splash or two of milk to help smooth out the mixture. Add just a little milk at a time to avoid a final product that is too runny.

Serve immediately, or freeze in an airtight container for at least 2 hours. Optional: sprinkle with cinnamon, drizzle with honey, or top with chopped nuts prior to serving.