1. Preheat the oven to 180°C. Coat a 23 x 23 cm baking dish with cooking spray.
2. Combine the flour, sugar, cocoa, baking powder and baking soda in a large bowl. Whisk together the buttermilk,
butter, eggs and vanilla extract in a medium bowl. Add to the flour mixture and stir to combine thoroughly without overmixing. Fold in the chocolate chips. Pour into the prepared pan.
3. Bake for 25 minutes, or until a wooden pick inserted in the centre comes out clean. Cool in the pan on a rack.