Preheat your oven to 350°F (175°C) and grease a 9x9-inch baking pan or line it with parchment paper.
In a mixing bowl, combine the mashed bananas and melted butter, mixing well until fully blended.
Add the brown sugar to the banana mixture and stir until well combined.
Incorporate the egg and vanilla extract, mixing until smooth.
In a separate bowl, whisk together the flour, baking powder, baking soda, and salt.
Gradually add the dry ingredients to the wet ingredients, stirring gently until just combined. Do not overmix.
Fold in the chocolate chips and walnuts if using, ensuring they are evenly distributed throughout the batter.
Pour the batter into the prepared baking pan and spread it evenly.
Bake in the preheated oven for 25-30 minutes, or until a toothpick inserted in the center comes out clean.
Let the blondies cool in the pan for about 10 minutes before transferring them to a wire rack to cool completely.
Once cooled, cut into squares and enjoy!
Notes
Serve on a decorative platter, optionally dusted with powdered sugar or drizzled with melted chocolate. Enjoy with fresh banana slices or vanilla ice cream!