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, cocoa powder, and instant espresso powder until well combined.
In a large bowl, whisk the melted butter and granulated sugar until smooth and combined.
Add the eggs one at a time to the butter and sugar mixture, whisking 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 using a spatula, mixing just until combined. Do not overmix.
Fold in the semi-sweet 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 with a few moist crumbs but no wet batter.
Remove the bread from the oven and let it cool in the pan for 15 minutes.
Use the parchment paper overhang to lift the bread out of the pan and transfer it to a wire rack to cool completely before slicing.