Place them in a ziploc bag and in the freezer for at least 1 hour. Meanwhile, prepare the caramel sauce if you haven't already.
Once the bananas have frozen, remove them from the freezer and into a food processor and pulse on high until bananas blend together and form a soft serve ice cream texture. This may take a few minutes and you may need to stop halfway through to scrape the sides down.
Pour ice cream in a nonstick or wax paper-lined bread pan; place back in the freezer for a minimum of 2 hours, but preferably overnight.
Once hardened, scoop ice cream into cups*, drizzle caramel sauce overtop and then pour freshly brewed espresso over ice cream.
*This recipe makes 4 cups with 2 scoops of ice cream each, or 6 cups with 1 scoop of ice cream each