Instructions

1. Preheat your oven to 190°C / 170°C Fan / Gas 5 / 375°F.
2. In a mixing bowl, add the caster sugar, cocoa powder and oil and mix for 2-3 minutes until all is combined.
3. To this add the egg and mix until smooth and shiny.
4. Add the sieved plain flour and baking powder and mix until combined.
5. Divide the cookie batter into 16, roll into balls and gently roll in the dish of icing sugar to coat.
6. Place the cookies on the lined trays and then into the centre of your preheated oven and bake for 10-12 minutes.
7. Once baked, allow to cool on a wire rack.
8. For the buttercream filling, simply whip the butter, vanilla and sugar together until smooth and creamy.
9. Place this into a piping bag and pip on the base of 8 cookies, place another cookie on top to sandwich and serve.