01 - Preheat the oven to 350°F. Grease a 9x5-inch loaf pan and line 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 blended.
04 - Beat in eggs, espresso, and vanilla extract until the mixture is smooth and uniform.
05 - Gently fold dry ingredients into the wet mixture until just combined. Avoid overmixing to maintain texture.
06 - Fold in the chocolate chips or chopped chocolate until evenly distributed throughout the batter.
07 - Transfer batter to the prepared loaf pan. Smooth the surface and sprinkle with extra chocolate chips if desired.
08 - Bake for 50-55 minutes until a toothpick inserted into the center emerges clean or with minimal moist crumbs.
09 - Allow to cool in the pan for 10 minutes, then remove to a wire rack to cool completely before slicing.