In a mason jar or bowl, combine the rolled oats, almond milk, cocoa powder, protein powder, and maple syrup. Stir well to combine.
Cover the jar or bowl with a lid or plastic wrap and place it in the fridge overnight (or for at least 6 hours).
In the morning, remove the jar or bowl from the fridge and stir the oats.
Top the oats with sliced banana, peanut butter, and chopped nuts.
Enjoy your delicious and satisfying chocolate overnight oats!