Add all of the ingredients into a blender in the order they are listed, except for the sprinkles.
Blend on low to break up the frozen banana. Slowly bring up the speed to medium, you should see a swirl going down toward the middle of the mixture (aka a vortex). Blend for at least a minute longer before bringing the blender to high and blending for another 25 - 30 seconds.
Pour into glasses and garnish with sprinkles if desired.
Notes
You can use any dairy alternative you like. Creamy cashew milk is particularly good here. The recipe is great doubled or halved.