Step 1Line a 10X8-inch brownie pan with greased foil, making sure you have enough overhang to lift out the brownies after baking.
Step 2Cream the brown, granulated and vanilla sugars with the butter or margarine in the bowl of an electric mixer.Blend in the eggs. Stir in the salt, cake meal and potato starch, then fold in the chocolate and nuts. Chill 20 minutes.
Step 3Meanwhile, heat the oven to 350 degrees.
Step 4Spread the batter into the pan. Bake the bars until the center is just set (not jiggly), about 35 to 40 minutes. Cool, then use the foil to lift from the pan. Cut the brownies into small squares.