Preheat the oven to 356º F (180° C) Linke a ramekin or round small cake pan of about 3.90 inches (10 cm) with parchment paper. You can also just grease it with butter and cover it with some flour.
Peel the banana, place it in a medium bowl and mash it with a fork until it is mashed. Add the egg, sugar, vanilla extract and beat well with the same fork so that everything is integrated.
Add the vegetable oil along with the milk, flour, baking soda and salt. If desired, chocolate chips can be added here. Beat again until you get a smooth and slightly lumpy mixture.
Pour the mixture into the ramekin and bake at 356º F (180º C) for 25 to 30 minutes until a wooden toothpick comes out clean when inserted and the top of the banana bread is golden brown.
Once ready, take the banana bread out of the oven and let it cool down in the same ramekin before turning it out. Let it completely cool down before eating.