Preheat oven at 350. Prepare a 13 x 23 cm baking pan with cooking spray lined with foil extending over edges to form handles. In a saucepan melt chocolate and margarine until chocolate is completed melted. In mixing bowl combine sugar and flour. Add egg whites, vanilla, and walnuts until well blended. Mix with chocolate margarine mixture. Spread in prepared pan. Bake for 30 to 35 minutes. Cool in pan. Refrigerate for 30 minutes for easier cutting. Lift out of pan with foil handles. Invert onto back of pan. Carefully remove foil. Invert onto cutting board. Cut into desired shapes with cookie cutter. Decorate as desired. NOTES : Decorate with icing, glaze, mini marshmallows, small candies, sugar crystals, or colored sprinkles. Recipe By : Baker's Unsweetened Chocolate