Preheat your oven to 350°F (175°C). Grease a muffin tin or line with paper liners.
In a large bowl, mix the oats, baking powder, salt, and cinnamon.
In another bowl, whisk together the mashed banana, milk, maple syrup, oil, and vanilla.
Pour the wet ingredients into the dry and stir just until combined.
Fold in any optional add-ins if using—no judgment if it's chocolate before 9am.
Scoop the batter evenly into the muffin cups.
Bake for 20 minutes or until the tops look set and spring back when touched.
Let them cool in the pan for 5 minutes before transferring to a wire rack.