01 - Preheat 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.
03 - In a large bowl, whisk mashed bananas, melted butter, sugar, eggs, and vanilla extract until smooth.
04 - Gently fold dry ingredients into wet mixture until just combined; avoid overmixing.
05 - Fold in chocolate chips and optional nuts evenly throughout the batter.
06 - Pour batter into prepared loaf pan and smooth surface.
07 - Bake for 50 to 60 minutes, or until a toothpick inserted in the center comes out with moist crumbs.
08 - Cool in pan for 10 minutes before transferring to a wire rack to cool completely; slice before serving.