Preheat the oven to 180C/350F/Gas 4, and line a baking tray with parchment paper, or a silicone mat. Set aside.
Whisk together the flour, oats, baking powder, baking soda, salt, and spices. Set aside.
Whisk together the melted butter and sugars until combined. Add the egg, banana, and vanilla, and mix until combined. Add the dry ingredients, and mix until just combined. Fold in the chocolate chips.
Roll the dough into 1.5oz balls (the dough should be sticky, but rollable), and place onto the prepared baking tray.
Slightly flatten the dough balls, and press the extra chocolate chips on top. Bake for 12 - 14 minutes until firm and golden brown around the edges.
Allow to cool on the baking tray for 5 - 10 minutes before transferring them to a wire rack to cool completely.
Video
Notes
Cookies stay fresh, kept in an airtight container, at room temperature or in the fridge for up to 1 week.Cookie dough balls can be kept in the fridge for up to 5 days, or frozen for up to 3 months. Bake from frozen.