Ingredients:
1 cup sugar
1/2 cup butter or margarine -- softened
1 teaspoon vanilla
2 eggs
2/3 cup all-purpose flour
1/2 cup baking cocoa
1/2 teaspoon baking powder
1/4 teaspoon salt
1/2 cup chopped walnuts, if desired

Directions:
Heat oven to 350º. Grease square pan, 9 × 9 × 2 inches. Beat sugar, butter, vanilla and eggs in large bowl with electric mixer on medium speed, or mix with spoon. Stir in remaining ingredients except walnuts.
Stir in walnuts.
Spread batter evenly in pan. Bake 20 to 25 minutes or until toothpick inserted in center comes out clean. Cool completely. Cut into 4 rows by 4 rows.