Cream the butter. Add the sugar and mix well. Add the egg, milk and vanilla and combine. Sift together 1 cup of the flour with the baking powder and mix it into the batter. Add some or all of the additional flour depending on how much the dough can handle. Form into a disk, cover in plastic and chill in the refrigerator at least 2 hours. Roll out on a lightly floured surface about 1/4-inch thick. Cut out hearts with various sized cookie cutters and place on a greased sheet pan. Bake at 375 degrees F for 8 to 10 minutes until very light golden brown. Let cool on the pan.
Icing: Whisk together the egg whites and powdered sugar to form a slightly loose icing. It should flow a little bit but not too much. Transfer a small amount to a separate bowl and add a tiny amount of red food coloring to make pink icing. Pipe a rim of pink icing around the edge of the cookie and then fill in the center with white icing, or just pipe decorative designs on the surface. Embellish with silver or gold balls. Let dry and package up in cello bags tied with a ribbon.
Consumption of raw or undercooked eggs, shellfish and meat may increase the risk of foodborne illness.