Preheat your oven to 350ºF. Oil a 9 x 5 loaf pan.
In a medium bowl, mash the bananas, then add in the egg, vanilla, sugar, and oil and stir together well. Set the bowl aside.
Put the flour, baking powder, baking soda and salt in another medium bowl. Stir together gently with a fork.
Add the dry ingredients to the wet ingredients all at once and stir together with a big wooden spoon—don't use an electric mixer! Stirring by hand just until everything is combined will prevent this from becoming gummy or tough. Once everything is just mixed together, add in the chocolate chips and mix again, lightly, just enough to spread the chips uniformly throughout the batter.
Spoon the batter into the loaf pan and put the pan in the hot oven. Set a timer for 55 minutes. Note that it may take as long as 65 minutes depending on your oven.
It’s done when the bread is just barely beginning to pull away from the sides and a tester inserted near the center comes out clean—but if, in the testing, you think you've stabbed a melty chocolate chip, wipe the tester and try again in a slightly different spot.
Set the bread, in the pan, on a rack to cool. After 10 or 15 minutes, carefully remove it from the pan and return it to the rack to finish cooling.