Step 1: Preheat the Oven to 350°F (175°C).

Step 2: In a large mixing bowl, whisk together the melted butter and brown sugar until smooth and creamy.

Step 3: Add the mashed very ripe bananas, egg, and vanilla extract, then stir vigorously until combined.

Step 4: In a separate bowl, sift together whole wheat flour, baking soda, and salt. Slowly fold into the wet mixture until just combined.

Step 5: If using, gently fold chocolate chips into the batter.

Step 6: Grease an 8x8 inch baking dish, pour the batter into the dish, and smooth the top.

Step 7: Bake for 30-34 minutes until lightly golden and a toothpick comes out with a few moist crumbs.

Step 8: Allow to cool for 5 minutes in the pan, then transfer to a wire rack to cool completely before slicing.