If you’re going to bake them right away, preheat your oven to 180°C/350°F and line a baking sheet with parchment or a silicone baking mat before starting.
In a small bowl whisk together the flour, baking soda, baking powder, salt and cinnamon.
In a separate bowl or flat plate for ease, mash the banana really well. It should be pretty smooth and have the texture of applesauce or baby food. Then add the oil, sugars, cornstarch and vanilla and whisk until smooth.
Add the dry ingredients along with the chocolate chips and stir just until well combined, avoid overmixing.
If you’re chilling the dough, cover it and place it in the fridge for at least 30 minutes or even overnight.
If not, scoop about 2-4 tbsp or 35-70 g worth of dough per cookie onto your prepared baking sheet, leaving room for spreading.
Bake for about 10 minutes or until the edges are golden brown but the middle is paler. They’ll still be soft and a bit underbaked but that’s normal, they’ll continue to bake as they cool on the tray. Let them cool about 5-10 minutes before transferring them to a wire rack (with a spatula if needed) to cool completely.