1. Preheat oven to 180°C. Line a baking tray with baking paper.
3. Transfer half the dough to a separate bowl and mix in cocoa and 1 Tbsp water.
4. To form a cookie, place alternating spoonfuls of the two mixtures into the palm of your hand and, using your other hand, gently swirl the mixtures and form into a rough ball (the mixture will be quite sticky). Place on prepared baking tray, tidying up the edges if need be. You will probably use ¼ cup of the mixture in total per cookie.
5. Repeat with remaining batter, until it has all been used up. You should have 6 cookies in total.
6. Bake for 10 minutes or until the cookies have expanded and risen, and a shell has formed. Bake longer if you prefer a crunchier cookie.