Preheat oven to 180 degrees C and grease a 20x20cm square cake tin.
Stir together the gluten-free flour mix, cornflour, white sugar, brown sugar, cocoa powder and bicarb soda in a bowl, sifting with a fork to remove lumps. Pour in the eggs and melted margarine and mix with a large spoon or electric mixer on low until the mixture forms a smooth batter, 3 to 5 minutes. Scrape the batter into the prepared cake tin.
Place a sheet of aluminium foil on the oven rack to prevent spills as the brownies rise then fall during baking. Bake until a toothpick inserted in the centre of the brownies comes out clean, 40 to 45 minutes.
. Absolutely loved it!! My sister and I thought it was great - didn't even notice it was gluten free. Will definable make it again
Just a note, when its still warm, it the texture feels under cooked but as it cools this is just the chewy fudge middle - 23 Sep 2012