Preheat oven to 350. Line baking sheet with parchment paper. Spray with PAM or other cooking spray.
In a large bowl, beat butter and both sugars together until creamy. Add vanilla, eggs, and mashed banana; combine until mixed thoroughly.
Beat in flour, baking soda, and salt until just mixed. Mix in 1 cup of chocolate chips.
Spread batter evenly onto pan and sprinkle top with remaining chocolate chips.
Bake for 18-22 minutes until golden brown. Your toothpick should come out clean. Maybe a few moist crumbs.
If the top browns too quickly, "tent" with some aluminum
If you can...let it cool and cut into squares.