Preheat oven to 350°. Grease 3 small 3" x 5 3/4" loaf pans; set aside.
In a small mixing bowl, whisk together flour, cocoa, baking powder, baking soda, and salt. Set aside.
In a large mixing bowl, whisk together oil, melted butter, brown sugar, egg, mashed bananas, and vanilla extract till well blended.
Add the dry ingredients to the banana mixture with 3/4 cup of the chocolate chips. Stir till just combined and divide between the 3 loaf pans.
Sprinkle the remaining 1/4 cup of chocolate chips on top of the loaves. Bake at 350° for 30-35 minutes or till toothpick inserted in the middle comes out clean.
Cool for 5-10 minutes in pans, then remove to cooling racks to cool completely.