Place the ingredients (except the optional toppings) into a blender.
Blend until very smooth.
Pour into bowls and top with optional toppings as you like.
Serve immediately.
Notes
Store any leftovers in an airtight container or reusable pouch for up to 24 hours. (It will have the consistency of drinkable yogurt as leftovers.) Or you can freeze it into popsicles.
This is intentionally thick so it's easy to eat with a spoon.) If it's too thick for your blender, add a little extra milk.)
Use dairy or nondairy milk.
Banana-free: Trade in 1 cup diced mango or use 1/2 cup yogurt instead.
Try letting the kids (even little ones!) add their own toppings for a fun food activity.