01 - Preheat the 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, mix the mashed bananas, granulated sugar, brown sugar, and melted butter until well combined.
04 - Beat in the eggs, espresso, and vanilla extract until smooth.
05 - Gently fold the dry ingredients into the wet mixture until just combined. Do not overmix.
06 - Fold in the chocolate chips or chopped chocolate.
07 - Pour the batter into the prepared loaf pan. Smooth the top and sprinkle with extra chocolate chips if desired.
08 - Bake for 50-55 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs.
09 - Let cool in the pan for 10 minutes, then transfer to a wire rack to cool completely before slicing.