In a large bowl, mash bananas with a fork. The riper the bananas the better. Then stir in oil, maple syrup, and oat milk until well incorporated. Substitutions: you can use honey instead of maple syrup if you are not vegan. Any plant milk should work.
Add flour, chia seeds, cinnamon, brown sugar, salt, baking powder, and baking soda.
Avoid overmixing! The batter should be well-combined but still lumpy.
Pour into a lined loaf pan, or silicone pan if you have it. Garnish top with slice bananas and extra chia. Bake at 190 degrees C for 60 min. Baking time can vary due to moisture. You can check the center by inserting a toothpick or knife. It should come out clean. Allow to cool for an hour before taking it out of the pan. Slice and enjoy!