Preheat oven to 180 degrees C. Grease a baking tray and set aside.
In a bowl, mix together the sugar, flour, cocoa powder, bicarb soda, baking powder and salt. In another bowl, mix the olive oil, soy milk, peppermint essence and vanilla. Slowly stir in the flour mixture.
Mix in the chocolate bits and baking chocolate then stir well. Pour into a greased baking tray. Bake in the preheated oven until a toothpick inserted into the centre comes out clean, about 30-45 minutes.
Allow to cool in pan then slice into squares and serve.