In a mixing bowl, combine the old-fashioned oats, mashed banana, ground cinnamon, vanilla extract, maple syrup, chia seeds, and coconut milk. Stir everything together thoroughly to ensure that the ingredients are evenly distributed and the banana is well incorporated. Cover the bowl with a lid or plastic wrap and refrigerate overnight to allow the oats to soak and flavors to meld.

Remove the soaked oats from the refrigerator and uncover. Give everything a gentle stir if needed, then divide the mixture between serving bowls. Sprinkle the raisins or other dried fruit pieces on top before serving. I like to add a few extra slices of banana for garnish—it adds fresh sweetness and looks beautiful too!