Slice and Freeze the Bananas. Start with 3–4 ripe bananas. Peel them, slice into ½-inch rounds, and place in a single layer on a parchment-lined baking sheet. Freeze for at least 2 hours, or preferably overnight, until solid.
Blend Until Creamy. Place the frozen banana slices into a high-speed blender or food processor. Pulse a few times to break them up, then blend until smooth and creamy. Scrape down the sides as needed. It will look crumbly at first, then suddenly turn into soft-serve ice cream. If your blender struggles, add a splash of plant-based milk to help the blades turn.
Add Mix-Ins (Optional). Once smooth, stir in any add-ins like chocolate chips, peanut butter, or cinnamon.
Serve Immediately or Freeze. Serve the banana ice cream right away for soft-serve consistency, or transfer to a freezer-safe container and freeze for 1–2 hours to scoop like traditional ice cream.