I'm glad I finally got around to it.
It's this recipe from The Kitchn - you freeze bananas and then blend them up in a food processor and they make lovely ice cream! It really has a nice creamy texture.
(It's a good recipe for me because I'm always buying a bunch of bananas, using a couple, and then the rest get too ripe - now I can just freeze them before that happens.)
It's easiest to cut the bananas into half-inch chunks before freezing them, and then let them sit out of the freezer for five or ten minutes before blending them up so they can soften a little.
In this batch, I added unsweetened cocoa powder - you don't really need sweetener since bananas are naturally pretty sweet but I bet chocolate chips or nutella would be delicious. Or peanut butter!
One banana is 100ish calories so definitely a good snack sized serving.