Pre-heat the oven to 160degC/320degF for fan/convection or 180degC/355degF for standard. For easy removal of the brownie, grease and line a 20 cm (8-inch) square pan with baking paper.
Chop chocolate in a small, heat-proof bowl. Microwave on high for one minute. Stir well. Continue to microwave for 30 seconds. Stir until smooth. Microwave for another 10 seconds to melt the mixture. Set aside.
In a large bowl, combine the sugars and softened butter. Use a whisk or a handheld electric mixer to combine the butter and sugar. Mix in the eggs one by one, beating well between each addition, until you have a pale, creamy mixture. Mix in vanilla, and mix until well combined.
Mix the melted chocolate with the flour and stir well. Mix in the cocoa powder, flour, and salt. Continue to stir until the batter becomes thick.
Spread the batter evenly in the prepared baking pan. Bake the brownie for between 30-35 minutes, or until it doesn't move when you move it. Let cool in the tin for about 30 minutes, then transfer to a wire rack to cool completely.
