Preheat oven to 350°F (175°C) and grease and line a 9x5-inch loaf pan
Whisk mashed bananas and melted butter in a large bowl
Add brown sugar and granulated sugar and whisk until combined
Whisk in eggs and vanilla until smooth
In a separate bowl, whisk flour, baking soda, salt, and cinnamon
Fold dry ingredients into wet mixture just until combined
Toss chocolate chips with flour and gently fold into batter
Pour batter into prepared pan and smooth the top
Sprinkle extra chocolate chips on top if desired
Bake for 55–65 minutes, tenting loosely with foil if browning too quickly
Cool in pan for 15 minutes, then transfer to a wire rack to cool completely