Preheat oven to 160 degrees C (320 degrees F). Place the egg whites in a clean dry bowl. Whisk with an electric mixture until soft peaks are formed. Then gradually add the sugar and 1 teaspoon of the cocoa powder while you continue whisking until stiff peaks are formed (about 10 minutes). The sugar should be incorporated and the mixture should appear nice and glossy. Fold through the remaining teaspoon of cocoa powder to create a bit of a swirl

Line a baking tray with baking paper. Using a spoon and your finger, take a spoonful of the mixture and push it off onto the tray with you finger and shape it into a rough ball. Dust with the extra cocoa powder and grate a little of the dark chocolate on top if using

Bake for 20 - 25 minutes. They should be crispy on the outside and cracks should be visible