Peel the first banana, place it in a microwave-safe bowl, and slit it down the middle. Try not to cut it the whole way through; you want to make a well more than two pieces of banana.
Fill up the well with a small handful of chocolate chips.
Cover the chocolate chips with a small handful of mini marshmallows.
Cook the banana boat in the microwave for 60 seconds. Very carefully (it will be hot!), take it out and look at it. Does the banana look mushy? The chocolate chips melted? Marshmallows softened? Then it's done. If it's not done, put it back in for another 30 or 60 seconds.
This is how we ate banana boats in the good old days. Let it cool a bit and eat. Never able to leave well enough alone, I added a step.