01 - Preheat oven to 350°F. Lightly grease two small ramekins or an oven-safe baking dish with cooking spray or a small amount of oil.
02 - In a medium bowl, whisk together rolled oats, cocoa powder, baking powder, and salt until evenly blended.
03 - In a separate bowl, mash the ripe banana thoroughly. Add milk, maple syrup (or honey), and vanilla extract. Whisk until smooth and fully combined.
04 - Pour the wet ingredients into the dry ingredients. Stir with a spatula or spoon until just combined, being careful not to overmix. Gently fold in chocolate chips and nuts if using.
05 - Divide the batter evenly between the prepared ramekins. Smooth the tops with the back of a spoon and sprinkle additional chocolate chips over the surface.
06 - Bake for 22-25 minutes until the oats are set and the tops appear slightly cracked. A toothpick inserted in the center should come out mostly clean.
07 - Let cool for 5 minutes in the ramekins. Serve warm, optionally drizzled with additional milk or topped with a dollop of yogurt.