Set the oven to 350°F and coat a 9-by-5-inch loaf pan with nonstick cooking spray. Prepare the pan before mixing so the batter can go straight into the oven once it is combined.

Whisk the flour, Dutch-process cocoa, baking soda, and sea salt in a medium bowl. Break up any cocoa lumps so the finished crumb looks evenly dark and smooth.

Mash the bananas in a large bowl, then stir in the melted butter and oil before adding the brown sugar, egg, and vanilla extract. Keep stirring until the wet mixture looks glossy and falls from the spoon in a thick ribbon.

Add the dry mixture to the banana mixture and fold just until no dry streaks remain, then fold in 3/4 cup of the chocolate chips. The batter should look thick and scoopable, not thin or heavily beaten.

Scrape the batter into the prepared pan, scatter the remaining 1/4 cup chocolate chips over the surface, and bake for 50 to 65 minutes. Start checking at 50 minutes, when the top should be set and the chocolate aroma should be especially rich.

Let the loaf rest in the pan on a wire rack for 15 minutes, then loosen the edges with a butter knife and lift it out carefully. You may feel slight resistance around the pan edges, which is normal before the loaf releases.

Cool the loaf on the wire rack until slightly warm before slicing, then wrap any remaining bread in plastic wrap. For freezing, cool completely, wrap in plastic wrap and aluminum foil, and defrost before slicing.