Begin by heating your oven to 350°F. Grease a 9-by-5-inch loaf pan with a light coating of nonstick cooking spray or line it with parchment paper.
In a medium bowl, whisk together the whole wheat flour, cocoa powder, baking soda, and sea salt.
Mash the ripe bananas in a large bowl until smooth, noting that riper bananas add more natural sweetness. Mix in the melted butter and applesauce, then add the coconut sugar, egg, and vanilla extract until smooth.
Gently fold the dry ingredients into the wet mixture. Remember, overmixing can lead to a denser bread. Fold in 1/2 cup of the dark chocolate chips, reserving the rest for topping.
Pour batter into prepared loaf pan, sprinkle remaining chocolate chips on top, and bake for 50-65 minutes until mostly clean toothpick. Start monitoring at 50-minute mark.
After baking, let bread cool in the pan on a wire rack for 15 minutes. Loosen edges with a knife, remove bread, and let it cool on the rack until just warm.