Meanwhile, in a mixer bowl, beat the cut up cream cheese and sugar until fluffy. Add the egg; beat to combine. Stir in chopped nuts, if desired. Pour the cream cheese mixture over partially baked layer. Carefully spoon the remaining brownie batter over cream cheese mixture.

To marble the brownies, use a narrow spatula to swirl through the light and dark layers, being careful not to touch the bottom layer. Return to the oven, bake 30-35 minutes more or until brownies test done. Cool in pan on a wire rack. Makes 24 bars.