Preheat oven to 350 degrees and line a 9x13 baking pan with parchment paper.
Using a standing mixer, beat together the butter, eggs, brown sugar, sugar, salt, and vanilla until combined and smooth.
Gradually beat in the flour and mashed banana until combined.
Fold in 2 cups of chocolate chips.
Pour the batter into the baking dish.
Sprinkle the remaining chocolate chips onto the top of the brownies.
Bake in the oven for 30-35 minutes or until a toothpick comes out of the center clean.
Allow to cool before cutting into bars.