Preheat the oven to 350°F (177°C).
Spray a 9×5-inch bread pan with non-stick cooking spray.
In a large bowl, mash thawed bananas with a fork or wooden spoon.
Add sugar, melted butter, egg and vanilla extract, and mix everything until combined.
Then add flour, cocoa powder, baking soda, baking powder and salt. Mix to combine.
Stir in chocolate chips, if using. Reserve some for the top as well.
Pour the batter into the prepared bread pan.
Bake for about 50 minutes, or until the inserted toothpick comes out clean. Cool completely before serving.