Preheat your oven to 350°F (175°C).

In a large mixing bowl, whisk together the melted butter and brown sugar until smooth and creamy, about 1-2 minutes.

Stir in your mashed very ripe bananas, the egg, and vanilla extract until fully combined and smooth, about 1-2 minutes.

Sift the whole wheat flour, baking soda, and salt over the wet mixture and gently fold until just combined.

Fold in the chocolate chips until evenly distributed.

Grease an 8x8 inch baking dish or line it with parchment paper. Pour the batter into the dish, spreading it evenly.

Bake for 30-34 minutes, checking for doneness with a toothpick.

Let the blondies cool in the pan for 5 minutes, then transfer to a wire rack to cool completely before slicing.