Cream the butter and sugar, I use my stand mixer for this but you can use a handheld beater or a wooden spoon and some elbow grease.
Add the banana and vanilla, my stand mixer beats the banana into the creamed butter and sugar, if you are making these cookies by hand you will need to mash the banana before adding it.
Add the flour, oats, baking powder and cinnamon. Mix until combined, I do this in the stand mixer.
Fold in the chocolate chips.
Optional: This cookie dough is easier to work with if you chill the dough for around 15-20 mins, but it is possible to make the cookies without chilling.
Heat your oven to 180 degrees celsius.
Scoop your cookie dough into 12 even portions, roll into balls, place on a lined baking tray, then flatten them gently with a fork
Bake at 180 degrees celsius for 10 minutes until lightly golden brown on the edges. The cookies will be soft, cool for 5 minutes before removing from the baking tray.