Heat oven to 325 degrees F. Grease and flour a 14 x 12-inch sheet cake pan.
Melt chocolate, 1/2 cup of the butter and all the margarine in top half of a
double boiler over boiling water, stirring to blend. When melted, remove from heat
and allow to cool. Sift together flour, baking soda and salt and set aside.
In a mixing bowl, beat 2 eggs and vanilla extract until frothy.
Add sugar and
continue bating until thick and lemon-colored.
Gradually beat in flour mixture until
Stir in chocolate mixture, scraping down sides of bowl as necessary.
When well blended, pour into prepared pan. Smooth top and sprinkle with 1/2 cup
of the walnuts. Set aside.
Beat cream cheese and remaining 1/2 cup butter until light and fluffy.
egg and beat to combine.
Add confectioners' sugar and beat until well blended.
Spread cream cheese mixture over top of brownies, leaving 1/2-inch border all around,
using a rubber spatula to smooth the surface.
Sprinkle with remaining 1/2 cup walnuts.
Bake for 30 to 40 minutes or until set.
Remove from oven and cool on a wire rack
for 2 hours before cutting into squares.