Preheat oven to 350 degrees F. Spray a 9x9-inch pan with cooking spray. In a medium bowl, whisk together flour, baking powder, baking soda and salt, set aside.
In the bowl of a stand mixer, fitted with the paddle attachment ( or in a medium bowl using a handheld electric mixer), cream together the butter and sugars until light and fluffy, 2-3 minutes, scraping down the sides of the bowl as needed.
Add the eggs and mix until combined. Add the bananas, vanilla and sour cream and mix well. Add the dry ingredients and mix until just blended. Stir in the chocolate chips.
Spread batter evenly into the prepared pan and bake 30 to 40 minutes, or until a toothpick inserted in the center comes out clean. Let cake cook completely and frost with chocolate frosting (if desired).