Prepare the Oven: Preheat the oven to 350°F (175°C). Line a standard 12-cup muffin pan with paper liners or lightly grease each cup.

Mix the Dry Ingredients: In a medium bowl, whisk together the flour, baking soda, baking powder, salt, and cinnamon until evenly combined.

Mash the Bananas: In a large mixing bowl, mash the bananas until mostly smooth with only a few small lumps remaining.

Mix the Wet Ingredients: Whisk the melted butter, brown sugar, and granulated sugar into the mashed bananas until smooth.

Add the eggs one at a time, mixing well after each addition. Stir in the vanilla extract and sour cream until fully combined.

Combine the Batter: Using a rubber spatula, gently fold everything together until no dry flour remains. The batter should be thick with a few small lumps. Avoid overmixing.

Fold in the Chocolate Chips: Gently fold in the chocolate chips until evenly distributed throughout the batter.

Fill the Muffin Pan: Divide the batter evenly among the prepared muffin cups, filling each about three-quarters full.

Sprinkle the reserved chocolate chips over the tops for a bakery-style finish.

Bake for 20–22 minutes, or until the tops are lightly golden and a toothpick inserted into the center comes out with a few moist crumbs but no wet batter.

Cool: Allow the muffins to cool in the pan for 5 minutes before transferring them to a wire rack.

Cool for another 5 minutes before serving.