Preheat the oven to 180oC and line a rectangular or square baking tray with a baking sheet.
In a large bowl, add your flour, bicarb of soda, baking powder, sugar, cacao, salt and choc chips. Mix together.
Mix the oil, butter and milk together in a small bowl.
Add your wet ingredients (oil etc) to the dry ingredients and mix thoroughly.
Your mixture should be soft and sticky like cake batter. If not, add a little more milk.
Transfer to your baking tray and cook for around 15 minutes. Be careful not to overcook, as the brownies will continue to cook for a few minutes after you remove them from the oven.