Preheat oven to 355°F (180°C) and line one 8x8" pan with parchment paper. Alternatively, you can grease the pan with butter. Set aside.
In a small bowl, mix the 2 tablespoons of flaxseed with 6 tablespoons of water then set aside to thicken for about 5 minutes. This will be your flax egg
Place the sugars and the water in a small pot on medium low and heat until all the sugar has dissolved. The syrup will be quite runny. Leave to cool for 5-8 minutes.
While waiting for the syrup to cool, mix all the dry ingredients together and create a well at the center. Pour in the olive oil, vanilla, flax egg and the cooled sugar syrup then mix until everything is just incorporated. P.S. A few lumps in the batter are perfectly ok.
If the batter is still very warm, wait for it to cool down*. Once cooled, add in the chopped chocolate, give it a quick mix then plop the batter into the pan. Sprinkle more chocolate on top. Bake for 30-35 minutes or until a toothpick inserted at the center comes out with a few moist crumbs (aka it will not be a clean toothpick but it shouldn't be wet either).
Leave the brownies to cool for 10 minutes in the pan then cool completely on a wire rack (or just slice into bars if you can't wait). Serve warm with a scoop of ice cream or a glass of milk. Enjoy!