Preheat oven to 350°F, grease 9x5-inch loaf pan with nonstick spray, and set aside.
In a medium bowl, sift together the flour, cocoa, baking soda, and salt. Set aside.
1 cup all-purpose flour, ½ cup unsweetened Dutch-process cocoa powder, 1 teaspoon baking soda, ½ teaspoon kosher salt
In a large bowl, combine the mashed bananas with the melted butter. Stir to combine.
3 ripe bananas, ½ cup unsalted butter
Add the brown sugar, egg, vanilla, and sour cream. Mix well.
1 cup brown sugar, 2 large eggs, 1 teaspoon pure vanilla extract, ½ cup sour cream
Gradually add dried ingredients to the large bowl of wet ingredients. Do not overmix.
Fold in the chocolate chips, reserving ¼ cup for the top of the bread.
1 cup bittersweet chocolate chips
Pour the batter into the prepared pan and sprinkle with the remaining chocolate chips.
Bake for 60 minutes. Oven times may vary. Check for doneness at 50 minutes, and every 5-10 minutes after that until a toothpick comes out batter free.
Allow to nearly completely cool to room temperature before removing from pan.