Preheat your oven to 350°F (175°C). Grease or line an 8x8-inch baking pan with parchment paper.
In a large mixing bowl, combine the mashed bananas, honey (or maple syrup), applesauce, and vanilla extract. Mix until well combined.
In another bowl, whisk together the oats, whole wheat flour, baking powder, baking soda, and salt.
Add the dry ingredients to the wet ingredients and stir until just combined. Fold in the dark chocolate chips or chopped nuts.
Pour the batter into the prepared baking pan and spread it evenly with a spatula.
Bake in the preheated oven for 20-25 minutes or until the edges are golden brown and a toothpick inserted into the center comes out clean.
Allow the bars to cool in the pan for about 10 minutes, then transfer them to a wire rack to cool completely before slicing into bars.