Peel your bananas and break them into chunks. If you have time, freeze them for at least two hours beforehand.
This is the single biggest pro-tip for a thick, creamy, non-watery smoothie.
Add the frozen banana chunks to your blender pitcher, followed by the milk, Greek yogurt, vanilla extract, and cinnamon.
Secure the lid on your blender. Start on a low speed and gradually increase to high. Blend for 45-60 seconds, or until the mixture is completely smooth and there are no banana chunks left.
Stop the blender, taste the smoothie, and decide if you want to add the optional honey or maple syrup.
Blend for another 10 seconds to incorporate.
Pour immediately into a glass, sprinkle a dash of cinnamon on top for aesthetic points, and consume. Don't let it sit, or it will start to separate—a tragedy we must avoid.