Peel the bananas and break them into chunks.
Toss them into a blender along with the peanut butter and milk.
Blend until it’s creamy and smooth—about 30 seconds.
Pour the mixture into popsicle molds (or small paper cups).
Insert sticks, then freeze until solid (at least 4 hours).
To unmold, run warm water over the outside of the molds for a few seconds, then gently pull the popsicles out.