Preheat the oven to 350°F (175°C). Grease a 9×5-inch loaf pan and line it with parchment paper, leaving an overhang on the sides for easy removal.
In a medium bowl, whisk together the all-purpose flour, baking soda, salt, unsweetened cocoa powder, and instant espresso powder until well combined.
In a large bowl, mix the melted unsalted butter, granulated sugar, and light brown sugar until smooth.
Add the eggs one at a time to the butter and sugar mixture, beating well after each addition.
Stir in the vanilla extract, mashed bananas, and sour cream until fully incorporated.
Gradually fold the dry ingredients into the wet ingredients, mixing just until combined. Do not overmix.
Fold in the semisweet chocolate chips evenly into the batter.
Pour the batter into the prepared loaf pan and smooth the top with a spatula.
Bake in the preheated oven for 55 to 60 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs.
Remove the banana bread from the oven and allow it to cool in the pan for 15 minutes.
Using the parchment paper overhang, lift the bread out of the pan and transfer it to a wire rack to cool completely before slicing.