Recipe adapted from Smitten Kitchen
3 medium large ripe bananas
1/2 cup unsalted butter, melted
3/4 cup brown sugar
1 large egg
1 tsp vanilla extract
1 tsp baking soda
1/4 tsp salt
1 cup all purpose flour
1/2 cup cocoa powder (I used Hershey's Special Dark)
1 cup (6 oz) semisweet or bittersweet chocolate chunks or chips
1/2 cup mini chocolate chips
Preheat the oven to 350 degrees and grease a 9x5" loaf pan with nonstick baking spray.
Mash bananas in a large bowl. Whisk in melted butter, then brown sugar, egg, and vanilla extract. Set a sifter or fine mesh strainer over the bowl and sift in the baking soda, salt, flour, and cocoa powder. Stir mixture with a wooden spoon until just incorporated. Then gently stir in the 1 cup of chocolate chunks or chips.
Transfer batter into prepared pan, sprinkle with mini chocolate chips, and bake 55 to 65 minutes, or until a cake tester comes out clean. Cool in the pan for 10 minutes, then transfer to a wire rack to cool completely. Keep bread wrapped tightly at room temperature for up to 4 days, or serve immediately.