Preheat oven to 180°C and grease a small baking tray. Blend chickpeas in a food processor or blender until smooth. Add flour, cocoa powder, baking powder, salt, sugar, milk and oil in food processor/blender and blend into a very smooth consistency. Add chopped walnuts and optional choc chips into mixture and stir thoroughly. Pour mixture into baking tray and bake for 20 minutes. Remove dish from the baking tray onto a rack and allow dish to cool down for 30 minutes. Once dish has cooled down, cut into bite sizes and enjoy.