Preheat your oven to 350°F.
Grease your loaf pan with butter.
Whisk together the flour, cocoa powder, baking soda, and sea salt and set aside.
Mash ripe bananas until mostly smooth. A fork works, but I like a potato masher to do the hard work faster.
Add the belted butter and oil into the banana and stir until combined.
Add the brown sugar, vanilla, and egg to the wet mixture and mix until combined.
Add the dry ingredients and stir. Get the big lumps out but don't over-mix, or you'll over-work the gluten in the flour.
Add ¾ of the chocolate chips to the batter and stir to mix.
Pour the batter into your loaf pan. Sprinkle the remaining chocolate chips on top.
Bake. It takes me in my oven about 55 minutes. Depending on your conditions, it can take anywhere from 50 to 65. Use the toothpick or knife blade method to test, and check several spots. Bread is done when the implement comes out clean-ish.
Remove from oven and place on cooling rack. Let cool for 15 minutes, then remove the loaf from the loaf pan to finish cooling. Slice and serve!