01 - Preheat the oven to 350°F. Line a 12-cup muffin tin with paper liners or lightly grease each cup.
02 - In a large bowl, whisk together mashed bananas, eggs, vegetable oil, brown sugar, and vanilla extract until smooth.
03 - In a separate bowl, combine all-purpose flour, baking powder, baking soda, salt, and ground cinnamon if using.
04 - Add the dry ingredients to the wet mixture and stir gently until just combined; avoid overmixing to maintain tenderness.
05 - Carefully fold in the semi-sweet chocolate chips and chopped nuts if desired.
06 - Distribute the batter evenly among the muffin cups, filling each about three-quarters full.
07 - Sprinkle a few additional chocolate chips atop each muffin before baking for a decorative touch.
08 - Bake for 18 to 22 minutes or until a toothpick inserted in the center comes out clean or with moist crumbs.
09 - Allow the muffins to cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.