Freezing bananas transforms them into a sorbetlike treat in this easy, healthy dessert. Make sure to use very ripe bananas with lots of brown spots.
Whirl bananas in a food processor until smooth and very creamy, 5 to 7 minutes, scraping down inside of bowl and letting them stand briefly if needed to soften.
Add flavorings and pulse a few seconds to blend. Transfer to an airtight container and freeze until firm enough to scoop, about 3 hours.
Make ahead: Up to 1 week, frozen airtight; if icy, let soften at room temperature briefly, then break into chunks and whirl in food processor until smooth.