Easy and quick, peanut butter optional!
Living as I do with other humans, 3am isn't the best time to go using the blender. This isn't as frothy and smooth as a blender-made shake would be, but you won't have to wash the blender either.
This won't work if your banana isn't ripe enough. It's best to use a banana that has a few brown spots on it and isn't too firm. If you need to, you can soften it a little by putting it in the microwave for a few seconds, but make sure not to cook it. You can also ripen it some by propping it near a heater, but that takes an hour or two.
Note: Photo is not my own. It might not even have banana in it. :)
Do not open the banana.
Mash it up inside the peel as much as you can, until the sides start to split some. Then squeeze the banana goo into your cup. Use a bowl if you are planning to whisk it in Step 6.
Now mash the banana with a fork as much as you can.
Add cocoa powder, sugar, and peanut butter if you'd like. Mix, and mash some more.
Use 1-2 tbsp sugar, or to taste. White and brown sugar are both fine. Raw turbinado sugar does not work because the crystals are too big. I'm sure honey is good too.
Now for the milk. Use 1 cup if you want a more milkshake-like consistency, 2 cups if you want a thick chocolate milk. Whole milk is probably best, but we never have it so I added 1 tbsp of half-and-half to some low fat. Thus defeating the purpose of low fat. ;)
Add the milk very slowly, stirring with your fork.
At this point, do not decide all of a sudden that after making this with 2 tbsp of cocoa powder for the past several weeks, you now think *more* is better and decide to throw it on top, making it impossible to mix in, and causing you to choke on cocoa powder with every sip.
Or, you could do that. Your call, right?
Additional steps, if you're a bit more ambitious:
Since there is no ice, you might like this to be colder. Stick it in the freezer for ten minutes, then stir again before drinking.
If you would like a frothier drink, use a bowl instead of a large cup and whisk vigorously before you drink.