Preheat the oven to 350°F (175°C). Grease a 9×5-inch loaf pan and set aside.
In a medium bowl, whisk together the all-purpose flour, baking soda, salt, cocoa powder, and instant espresso powder until well combined.
In a large bowl, mix the melted butter and granulated 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 add the dry ingredients to the wet ingredients, stirring gently until just combined. Do not overmix.
Fold in the semisweet chocolate chips evenly throughout the batter.
Pour the batter into the prepared loaf pan and smooth the top with a spatula.
Bake for 55 to 65 minutes, or until a toothpick inserted into the center comes out clean or with just a few moist crumbs.
Remove the banana bread from the oven and let it cool in the pan for 10 minutes.
Transfer the bread to a wire rack to cool completely before slicing and serving.