Preheat your oven to 325 degrees Fahrenheit and grease a standard (9-inch by 5-inch) loaf pan with butter, lining it with parchment paper if desired.
In a large mixing bowl, mash the bananas with a fork until no large pieces remain.
Add the sugar, egg and oil and mix with a wooden spoon until everything is incorporated.
Measure the flour, baking powder, baking soda and salt into a separate mixing bowl and stir them together with a fork. Once they’re mixed together, dump the dry ingredients into the wet ingredients.
Using a wooden spoon, carefully mix the wet and the dry ingredients together. The danger here is over-mixing which will result in a dense, flat and dry loaf. The best technique for mixing is to scoop underneath the mixture and pull up gently instead of stirring around in a circle (like you’d stir your coffee, for example). Continue mixing this way just until the dry ingredients have been incorporated. It’s fine if there are a few small streaks of flour in the batter; it’s the large pockets of flour you want to make sure are incorporated.
Add the chocolate chips and stir them in gently, just until incorporated.
Pour the batter into the prepared loaf tin, smoothing it out on top.
Bake the loaf in the oven at 325 degrees for about 45-55 minutes (depending on your oven), or until it's golden brown on top and a toothpick inserted into the center of the loaf comes out clean.
Let it cool in the loaf pan for about 10 minutes and then lift it out of the pan using the parchment paper (or turn it out gently if you didn't use the parchment paper) to cool completely on a wire rack.
Slice and enjoy!