Preheat oven to 350°F. Grease 9×9-inch baking pan. Melt chocolate and butter in small saucepan over medium-low heat, stirring frequently. Combine sugar, flour, eggs, TABASCO® Sauce and melted chocolate mixture in large bowl until well blended. Stir in chocolate chips and walnuts. Spoon mixture into prepared pan. Bake 35 to 40 minutes or until toothpick inserted in center comes out clean. Cool in pan on wire rack.