Preheat the oven to 350°F (180°C) and line a loaf pan with parchment paper. Set aside.
In a large bowl, mash the bananas with a fork until very smooth. Add the olive oil, cane sugar, brown sugar, milk, and vanilla. Stir until well combined.
Add the flour, cinnamon, baking powder, baking soda, and salt into the bowl. Stir until just combined.
Gently fold the walnuts and chocolate into the bowl, mixing until evenly distributed.
Pour the batter into the prepared loaf pan and bake for 60-70 minutes, or until the top springs back when lightly touched.
Cool for 10 minutes in the pan before removing and cooling fully on a rack. This loaf keeps well in a sealed container for up to 3-4 days at room temperature, or up to a month in the freezer.
Notes
If your pan is longer and narrower than usual, the baking time might vary slightly from what’s suggested in the recipe card. Since this also depends on actual temperature of your oven, it’s a good idea to do a toothpick test in any case.