Preheat the oven to 350°F (175°C). Grease an 8×8-inch baking pan or line it with parchment paper.
In a large mixing bowl, combine the mashed bananas and melted butter. Stir until smooth.
Add the granulated sugar, eggs, and vanilla extract to the banana mixture and whisk until well combined.
In a separate bowl, sift together the all-purpose flour, cocoa powder, baking powder, and salt.
Gradually add the dry ingredients to the wet ingredients, stirring gently until just combined. Do not overmix.
Fold in the semi-sweet chocolate chips evenly throughout the batter.
Pour the batter into the prepared baking pan and spread it out evenly.
Bake in the preheated oven for 28-30 minutes, or until a toothpick inserted into the center comes out with a few moist crumbs.
Remove from the oven and let cool completely in the pan on a wire rack before cutting into 12 squares.
Serve and enjoy your banana bread brownies!