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, cocoa powder, baking powder, baking soda, cornflour, salt, and spices. Set aside.
Whisk together the butter and sugars until combined. Add the egg and vanilla, and mix until combined.
Add the dry ingredients, and mix until just combined. Fold in the chocolate chips.
For the Sugar Coating
In a small bowl, mix together the sugar and cinnamon.
Roll the dough into 1.5oz balls, roll them in the sugar mixture until evenly coated, then place onto the prepared baking tray.
Bake for 10 - 12 minutes or until firm and cracked on top. Allow to cool on the baking tray for 5 - 10 minutes before transferring to a wire rack to cool completely.
Video
Notes
Cookies stay fresh, kept in an airtight container, at room temperature 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.