Add the milk, oats, and peanut butter into a container that has a lid. Use a fork or the back of a spoon to mash the peanut butter into the oats and combine it with the milk until mixed well.
Add in the banana slices and mash to combine the banana into the oat mixture. Add the rest of the ingredients, combine well, put the lid on, and allow the mixture to sit overnight in your fridge.
In the morning, spoon the oats into a bowl (or eat straight from the container!) and add more sliced banana and chia seeds for a garnish.