Paola Velez adds her own spin to the iconic New York City treat of her youth: the Black and White cookie. She starts by going all-chocolate with the topping: one side gets piped with dark chocolate ganache and the other with ruby chocolate, a fruity chocolate with a pink hue. Velez also swaps traditional whole milk for buttermilk, which helps the baking soda activate, leading to a tender, well-risen cookie. A touch of rye flour in the dough is not only a nod to iconic NYC deli breads, its savory, nutty flavor helps balance the sweetness of this classic cookie. Finally, she adds gold leaf to the finished cookies for a fun metallic shine. To apply the gold leaf, she brushes it on in little dabs, using a small artist's paint brush.