01 - Preheat oven to 350°F. Grease and flour a 9x5-inch loaf pan or line with parchment paper.
02 - In a medium bowl, whisk together flour, cocoa powder, baking soda, and salt. Set aside.
03 - In a large bowl, combine mashed bananas, melted butter, sugar, eggs, vanilla extract, and espresso. Whisk until smooth.
04 - Gradually fold the dry ingredients into the wet mixture until just combined—do not overmix.
05 - Gently fold in the chocolate chips.
06 - Pour the batter into the prepared loaf pan and smooth the top.
07 - Bake for 50–60 minutes, or until a toothpick inserted into the center comes out with moist crumbs (not wet batter).
08 - Allow to cool in the pan for 10 minutes, then transfer to a wire rack to cool completely before slicing.