Prepare the pan: Line a 9x5 loaf pan with a parchment paper sling and secure it with binder clips.
Mix the dry ingredients: In a medium bowl, whisk together the flour, cocoa powder, sugars, baking soda, and salt until well combined. Set aside.
Melt the butter: In a small bowl, microwave the butter for about 30 seconds, or until fully melted. Set aside.
Preheat the oven: Set your oven to 350°F (175°C) while you prepare the batter.
Mash the bananas: In a large bowl, mash the ripe bananas with a fork until smooth. Add the eggs, sour cream, oil, melted butter, and vanilla extract into the same bowl. Whisk everything together until fully incorporated.
Combine wet and dry ingredients: Add the dry ingredients to the wet mixture, folding gently with a rubber spatula until just combined. Then, fold in the chocolate chips.
Fill the pan: Pour the batter into the prepared loaf pan, spreading it evenly.
Bake: Place the pan in the oven and bake for 60 minutes, or until a toothpick inserted into the center comes out clean.
Cool and remove: Let the banana bread cool in the pan on wire rack to cool completely. Once completely cooled, use a butter knife to loosen the edges without parchment paper. Remove from the pan and slice. Enjoy!
Optional ganache topping: For the ganache, heat the heavy cream in a small microwave-safe bowl until warm (about 30 seconds). Add the finely chopped chocolate, making sure the warm cream covers it, and let it sit for 1 minute. Stir with a small spatula or spoon until smooth and glossy. Drizzle or pour the ganache over the cooled banana bread. Once the ganache sets, slice and enjoy!