Prep: Preheat oven to 350°F (175°C). Grease a 9x5-inch loaf pan or line with parchment paper.
Wet Ingredients: In a bowl, mash bananas. Add sugars, melted butter, egg, and vanilla. Mix well.
Dry Ingredients: In another bowl, whisk flour, cocoa powder, baking soda, and salt.
Combine: Gently fold dry ingredients into wet ingredients until just combined. Stir in chocolate chips.
Bake: Pour batter into the loaf pan. Top with extra chocolate chips. Bake for 50–60 minutes (or until a toothpick comes out clean).
Cool: Let cool in the pan for 10 minutes, then transfer to a wire rack.