Preheat oven to 350°F. Spray a 9 x 5 inch loaf pan with baking spray. Set aside.
In a medium mixing bowl, use a whisk to sift together flour, cocoa, baking soda and salt.
In a separate bowl use a fork to mash bananas. Whisk in buttermilk, granulated sugar, brown sugar, butter, egg and vanilla.
Add wet to dry ingredients, mixing by hand with a large spoon or spatula until fully moistened. Mix in 3/4 cup chocolate chips.
Spread into prepared pan. Sprinkle top with reserved chocolate chips. (You may use more chocolate chips on top, if desired)
Bake for 50-60 minutes or until a toothpick inserted into the center shows moist crumbs.
Cool in pan for 15 minutes then remove to a cooling rack to cool completely.
Store at room temperature or chilled tightly wrapped for up to 3 days.