Mix butter, eggs, sugars, salt and vanilla with an electric mixer until well mixed.
Add flour, mashed banana and baking melts (or chocolate chips).
Stir with a wooden spoon to combine.
Spray a 9×13” glass baking dish with cooking spray.
Spread brownie mixture into prepared pan.
Smooth the top with a knife or rubber spatula.
Sprinkle chocolate chips on top.
Bake at 350° for 30-40 minutes just until lightly golden brown, and a toothpick inserted in center comes out clean.
Cool completely before cutting into bars.