IN saucepan over med-high heat, bring sugar, butter and 2 tbsp water to boil. Mix well. Remove from heat and stir in half of the bittersweet chocolate. Whisk until melted and let cool for 10 minutes. Whisk in eggs, 1 at a time, whisk in vanilla.

In separate bowl, whisk together flour, baking soda and salt. Stir into chocolate mixture. Stir in remaining chocolate (all).

Pour into parchment lined 9-inch square metal cake pan.

Bake in centre of 325F oven for 30 minutes or until tester inserted in centre comes out almost clean.

Let cool on rack.