Preheat your oven to 350°F (175°C) and prepare an 8-inch square baking pan by lining it with parchment paper or greasing it lightly.

In a large mixing bowl, mash the overripe bananas until smooth, leaving a few small lumps for texture. Then, stir in the melted unsalted butter, whisk in the brown sugar, egg, and vanilla extract until well-combined.

Sift together the all-purpose flour, baking soda, and salt in a separate bowl to ensure an even distribution.

Gradually add the dry mixture to the wet banana mixture, folding gently with a spatula. Stir in chocolate chips or nuts if desired.

Pour the batter into the prepared baking pan, spreading it evenly. Bake for 20-25 minutes until the edges are set and a toothpick comes out clean.

Let the blondies cool in the pan for about 10 minutes, then lift them out using the parchment paper and cool completely on a wire rack.