Bananas should be very ripe and with a dark brown peel. You don't want to buy fresh bananas from the grocery store for this recipe, but rather, let them sit on the counter and develop brown, even black, spots. You'll want no green on the banana or its stem—and there's a reason for this. As a banana ripens, the starches break down into sugar. This breakdown makes them perfect for baking and increases their antioxidant levels. The mushy texture also makes them malleable (ideal for mixing) and provides the loaf that desirable soft mouthfeel.