Preheat oven to 325 degrees.
Combine sugar, egg substitute, kahlua, and melted margerine in a large bowl, stirring well.
Combine flour, cocoa, and baking powder. Stir into sugar mixture.
Fold in walnuts.
Spoon batter into 9 inch square pan coated with cooking spray.
Bake for 30-35 minutes or until a wooden toothpick inserted in center comes out clean.
Cool in pan on a wire rack. Cut into squares.