Heat oven to 350. Spray lightly a 9" cake pan w/ cooking spray. In microwaveable bowl, place chocolate and butter. Microwave, stirring, until smooth.
In another bowl, Stir together 1/2 cup sugar and 4 egg yolks, mix well. Add to melted chocolate. Mix well.
In another bowl, beat 4 egg whites and remaining sugar until stiff peaks form. Fold into chocolate mix. Pour into pan. Bake 40 mins, or until a toothpivk inserted in center comes out clean. Serve topped w/ fresh berries.