#1. Line 15x10x1-inch pan with foil lightly grease foil. Set aside. Melt butter in large saucepan on low heat. Add marshmallows cook until melted, stirring frequently. Remove from heat. Add cereal mix well. Press firmly into prepared pan cool completely. #2. Remove formed cereal mixture from pan by turning pan upside down on cutting board. Remove pan peel off foil. Cut cereal mixture crosswise in half. Spread one half with dulce de leche top with remaining half to form sandwich. #3. Decorate with icing, if desired. Cut into 24 squares to serve.