Preheat your oven to 350°F (175°C). Grease a 9x9-inch baking pan lightly with oil or butter, or line it with parchment paper for easy removal of the bars after baking.
In a large mixing bowl, combine the mashed ripe bananas, unsweetened applesauce, packed brown sugar, honey or maple syrup, and pure vanilla extract. Use a fork or whisk to mix until the mixture is smooth and well-blended.
Evenly sprinkle the baking soda, sea salt, and ground cinnamon over the wet banana mixture. Stir gently to ensure all the dry ingredients are incorporated into the batter.
Gradually add in the whole wheat flour, mixing gently with a spatula or wooden spoon until just combined. Avoid overmixing to maintain a chewy texture.
Gently fold in the semi-sweet chocolate chips and chopped walnuts (if using) until they are evenly distributed throughout the batter.
Pour the batter into the prepared baking pan. Use a spatula to spread the batter evenly, reaching the corners of the pan.
Bake in the preheated oven for 25-30 minutes. Check for doneness by inserting a toothpick into the center; it should come out clean or with just a few moist crumbs attached.
Once baked, allow the bars to cool in the pan for about 10 minutes. Carefully lift them out using the parchment paper if used, and place them on a wire rack to cool completely before cutting into squares.
Notes
For a delightful presentation, cut the bars into squares and arrange them on a vibrant platter. Drizzle a little melted chocolate over the top for an enticing finish.