- HEAT oven to 350ºF. Line 13×9-inch baking pan with foil; set aside.
- COMBINE 1 cup flour and sugar in large bowl; cut in butter until crumbly. Press on bottom of pan. Bake 15 minutes.
- COMBINE sweetened condensed milk, cocoa, egg, remaining 1/4 cup flour, vanilla and baking powder in medium bowl. Mix in chocolate pieces and nuts. Spread over prepared crust. Bake 20 minutes or until set.
- COOL. Use foil to lift out of pan. For hearts, cut with heart-shaped cookie cutter or with knife, cut around waxed paper heart shape. Can also be cut into bars. Decorate with icing or gels, if desired. Store leftovers covered.