Preheat the oven to 180°C and line 2 large baking trays with baking paper.

In a large bowl, beat dairy-free butter, brown and white sugar and vanilla until creamy with an electric hand mixer or a stand mixer with the paddle attachment fitted. Add in the egg and vanilla extract and continue to beat until mixed through.

In a separate bowl, sift flour, cocoa powder and bicarb together and stir to combine. Add the dry ingredients to the wet, and continue to beat until a dough forms.

Using a tablespoon or a cookie scoop, roll balls of dough before first rolling the dough ball in a small bowl of white sugar to coat, and then into a bowl of icing sugar, until the outside of the ball is coated.

Place the balls of dough evenly apart on the baking tray, ensuring there is enough space for the cookie to spread. Bake for 10 minutes or until the edges are just crisp and the middles are still soft. Let them cool on the tray for 10 minutes to set before transferring to a wire rack to cool completely.