Preheat oven to 325 F. Grease and flour a 9 x 9 baking pan.
In a large glass bowl, melt the butter in the microwave. Stir in white sugar, brown sugar and corn syrup.
Beat in eggs and vanilla. Gently stir in cocoa powder, salt and flour.
Bake for 25 for 30 min or until a few crumb cling to an inserted toothpick.
Cool completely before cutting into bars.