Preheat your oven to 350°F (175°C) and grease a 9x9-inch baking pan or line it with parchment paper for easy removal.
In a large mixing bowl, combine the mashed bananas and melted butter until well blended.
Stir in the granulated sugar, followed by the eggs and vanilla extract, mixing until smooth.
In a separate bowl, whisk together the flour, cocoa powder, baking soda, and salt.
Gradually add the dry ingredients to the banana mixture, stirring until just combined. Be careful not to overmix.
If using, fold in the chocolate chips for added richness.
Pour the batter into the prepared baking pan and spread it evenly.
Bake for 25-30 minutes, or until a toothpick inserted in the center comes out clean.
Allow the brownies to cool in the pan for about 10 minutes before transferring them to a wire rack to cool completely.
Cut into squares and enjoy!