Heat the oven to 325 degrees F (163 degrees C) and line or grease a 9x5 nonstick loaf pan.
Mash the bananas with a fork until mostly smooth; small lumps are fine.
Lightly beat the eggs, then combine bananas, oil, eggs, and sugar in a large bowl. Stir until fully blended.
Add flour, vanilla, baking soda, baking powder, and salt. Stir with a large spoon just until combined - an electric mixer overmixes and turns the crumb gummy.
Optional: fold in a cup of chocolate chips or chopped walnuts last.
Scrape the batter into the pan and smooth the top.
Bake at 325 F (163 C) for 65 to 70 minutes, until the internal temperature reaches 200 to 205 degrees F.
Cool in the pan for 10 minutes - do not lift it out during this rest - then turn onto a rack. Full cooling can take 1 to 2 hours.