Peel and cut the bananas into 1-inch rounds. Place the bananas in a freezer bag and freeze for at least 3 hours.
In a small bowl, whisk together the cocoa powder, milk and vanilla.
If your banana slices have been frozen for longer than a day, let them thaw for about 15 minutes. Place the frozen bananas, chocolate mixture and salt in a food processor and blend well, stopping to scrape down the sides often to get a smooth, even consistency. Add a drop of mint extract to the ice cream, blend and taste. For a more intense mint flavor, increase the mint a drop at a time until you achieve the desired taste. Finally, add the chocolate chips into the ice cream and stir by hand until they're mixed throughout.
Scoop the ice cream into single-serving bowls and serve immediately or cover in plastic wrap and freeze. If you're saving these for a later time, remove the bowls from the freezer about 5 minutes before serving.