In a jar or sealed container, combine oats, milk, yogurt, mashed banana, maple syrup (if using), chia seeds, vanilla, cinnamon, and salt. Stir well to fully incorporate the banana.

Cover the container and refrigerate for at least 4 hours—or ideally overnight—to let the oats soak and thicken.

In the morning, enjoy as is or warm it gently. Optionally, top with sliced banana, chopped walnuts or pecans, nut butter, or extra sweetener.