Preheat the oven to 350ºF and position the rack in the center. Grease a 9×5-inch loaf pan with non-stick spray or line with parchment paper.
In a large bowl, whisk together the flour, granulated sweetener, chocolate protein powder, cocoa powder, cornstarch, baking soda, and salt.
In a separate medium bowl, mash the bananas until completely smooth.
Add the egg, olive oil, yogurt, and vanilla extract to the mashed bananas and whisk until fully combined.
Pour the wet ingredients into the dry ingredients and mix until well incorporated. Do not overmix.
Fold in the chocolate chips evenly throughout the batter.
Pour the batter into the prepared loaf pan and spread evenly. Sprinkle extra chocolate chips on top if desired.
Bake for 50–60 minutes, or until a toothpick inserted into the center comes out clean or with a few moist crumbs (around 55 minutes is ideal).
Let the bread cool in the pan for 10 minutes, then transfer to a wire rack to cool completely before slicing.
