Preheat the oven to 425°F (220°C).
In a mixing bowl, combine mashed bananas, melted butter, brown sugar, granulated sugar, sour cream, egg, and vanilla extract. Whisk until well combined.
In a separate bowl, sift together flour, baking soda, baking powder, and salt.
Add the dry ingredients to the wet ingredients and mix until just combined. Do not overmix.
Fold in chocolate chips.
Grease 6 jumbo-sized muffin tins and line with cupcake liners.
Scoop the batter into prepared muffin tins, filling about ¾ of the way.
Bake for 5 minutes at 425°F (220°C), then reduce the oven temperature to 375°F (190°C) and continue baking for an additional 15 minutes, or until the muffins are cooked through.
Remove from the oven and allow to cool before serving.
