Add the mashed banana, water, oats, dates, vanilla, and cinnamon to a small pot over medium heat. Bring to a simmer and cook for about 5 minutes, giving a stir every now and then until the oats are tender and most of the water is absorbed.
Divide among 2 bowls and top with the banana slices, chocolate chips, walnuts, and a drizzle of non-dairy milk.