Preheat your oven to 350°F (175°C) and line a muffin tin with paper liners or grease it lightly.
In a large bowl, combine the rolled oats and milk. Let it sit for about 10 minutes to allow the oats to absorb the liquid.
Add the mashed banana, honey or maple syrup, vegetable oil, and vanilla extract to the oat mixture. Stir until well combined.
In a separate bowl, whisk together the baking powder, baking soda, salt, and ground cinnamon.
Gradually add the dry ingredients to the wet mixture, stirring until just combined. Be careful not to overmix.
Fold in the chocolate chips gently.
Divide the batter evenly among the muffin cups, filling each about 2/3 full.
Bake for 18-20 minutes or until a toothpick inserted into the center comes out clean.
Allow the muffins to cool in the pan for 5 minutes before transferring them to a wire rack to cool completely.