Preheat the oven to 350F. Spray a 9X5 loaf with non stick baking spray. Line the pan with parchment paper to make it easier to get out of the pan.
In a medium bowl, sift together the flour, cocoa powder, baking soda and salt. Set aside.
In a small bowl, use a fork or potato masher to mash the 3 ripe bananas.
In a medium bowl, whisk the melted butter and brown sugar until a thick paste forms. Add in mashed bananas, sour cream, and vanilla. Mix together until combined.
Add in eggs one at a time and mix thoroughly. Add in all of the dry ingredients and mix until all combined. The batter will be slightly lumpy because of the bananas. Add all of the chocolate chips.
Pour the batter into the loaf pan. Fill the pan ¾ths of the way. If you have extra batter you can put it in a muffin pan. Sprinkle extra chocolate chips on top of batter.
Bake the banana bread for 50-60 minutes. The banana bread is finished baking when a toothpick inserted comes out clean. Let the banana bread sit for 10 minutes in the pan, then transfer to a cooling rack. Let the banana bread cool completely before serving. Store banana bread covered at room temperature.