01 - Preheat oven to 350°F. Line a 12-cup muffin tin with paper liners or coat with nonstick spray.
02 - In a large mixing bowl, whisk together mashed bananas, melted butter, sugar, eggs, and vanilla extract until smooth.
03 - In a separate bowl, whisk together all-purpose flour, baking soda, baking powder, and salt.
04 - Gently fold dry ingredients into wet mixture using a spatula until just combined, being careful not to overmix.
05 - Fold chocolate chips into batter, reserving a small handful for topping if desired.
06 - Divide batter evenly among muffin cups, filling each approximately 3/4 full. Top with reserved chocolate chips.
07 - Bake for 18-22 minutes until a toothpick inserted into the center emerges clean or with a few moist crumbs.
08 - Cool muffins in tin for 5 minutes, then transfer to a wire rack to cool completely.