01 - Preheat the oven to 350°F. Grease and line a 9x5-inch loaf pan with parchment paper.
02 - Whisk together flour, cocoa powder, baking soda, and salt in a medium bowl. Set aside.
03 - Combine mashed bananas, granulated sugar, brown sugar, and melted butter in a large bowl until well incorporated.
04 - Beat in eggs, espresso, and vanilla extract until the mixture is smooth and uniform.
05 - Gently fold dry ingredients into wet mixture until just combined. Avoid overmixing to prevent tough texture.
06 - Fold in dark chocolate chips until evenly distributed throughout the batter.
07 - Pour batter into prepared loaf pan, smooth the top, and optionally sprinkle with additional chocolate chips. Bake for 50-55 minutes until a toothpick inserted in the center comes out clean or with a few moist crumbs.
08 - Let the bread cool in the pan for 10 minutes, then transfer to a wire rack to cool completely before slicing.