01 - Preheat oven to 350°F. Grease and line a 9x5-inch loaf pan 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, granulated sugar, brown sugar, and melted butter until well incorporated.
04 - Beat in eggs, espresso, and vanilla extract until 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 or chopped chocolate until evenly distributed.
07 - Pour batter into prepared loaf pan. Smooth top surface and sprinkle with additional chocolate chips if desired.
08 - Bake for 50-55 minutes until toothpick inserted into center emerges clean or with minimal moist crumbs.
09 - Allow to cool in pan for 10 minutes, then transfer to wire rack to cool completely before slicing.