Preheat the oven to 170°C. Line 2 large baking sheets with baking paper and grease with nonstick spray.
1. Dough Beat the butter and sugar until light and creamy. Beat in the eggs one at a time, then add the vanilla essence.
2. Sift the flour, cocoa powder, baking powder, bicarbonate of soda and salt over and mix until the dough is smooth.