Preheat oven to 350 degrees. Mash the bananas with a fork in a small bowl and set aside. Cream the butter using a hand mixer and add the sugar, continue mixing until light and fluffy in texture. Add in the eggs, and mix well. Add in the mashed bananas and the vanilla. Finally, add in the flour and baking soda and stir just until mixed well. Fold in the chocolate chips if using. Transfer the batter to a loaf pan that has been sprayed with cooking spray. Bake for 1 hour or until a toothpick inserted into the bread comes out clean. Let cool for 10 minutes before removing from the loaf pan onto a cooling rack. Classic Banana Bread tastes wonderful still warm with a nice layer of butter!