Line a 9×5 loaf pan with parchment paper, making sure the parchment is hanging over the sides of the loaf pan. Spray with nonstick spray and set aside.
Cream butter and sugar together until smooth. Mash the bananas with a fork then stir them into the batter. Whisk in the egg and add in the vanilla. Mix until well combined.
Add the flour, baking soda, baking powder, and salt. Make sure the flour is not clumpy. Mix until just combined. Careful not to over mix. Using a spatula, fold in the chocolate chips and/or walnuts.
Pour the batter into the loaf pan and sprinkle some chocolate chips on top. Bake for 55-65 min until a toothpick inserted in the center of the loaf comes out clean. Let cool for at least 30 min before serving.