Preheat oven to 350°F, line a 8x8 or 9x9 baking pan with parchment paper and set aside.
With your mixer mix both sugars and butter on med-high speed for about 5 mins. making sure to scrape down the sides in between.
Add your egg and vanilla and mix for another min. Then add your mashed banana.
With mixer on low speed add your salt and flour and mix until just combined.
Fold in your chocolate chips.
Pour batter into prepared baking pan and place in oven to bake for 30-35 mins., until edges are golden brown and toothpick inserted comes out a little wet still.
Let cool in pan for 15 mins. before removing and transferring over to cooling rack. Cool for another 25-30 before cutting into.