Special equipment: 2 1/2-by-3-inch heart-shaped cookie cutter
Sift together flour, baking powder, and salt. Place butter and sugar in the bowl of a standing mixer and beat until light in color. Add the red food coloring, egg and milk and beat to combine. Proceed with recipe and chill for 2 hours.
Preheat the oven to 375 degrees F.
Sprinkle a work surface and rolling pin with confectioner's sugar and roll out dough to 1/4-inch thick. Move dough frequently to prevent it from sticking and add more confectioner's sugar to the work surface and rolling pin as needed. With a 2 1/2-by-3-inch heart-shaped cookie cutter, cut 36 hearts, re-rolling dough as needed. Place at least 1 inch apart on parchment-lined baking sheets, and bake until cookies are set but not brown, about 7-8 minutes. Let cool on the pan slightly before transferring to a rack to cool completely.
To make striped Valentine hearts, transfer half of the melted chocolate to a disposable pastry bag, twist the end closed, and using scissors, snip a very small opening in the tip. Starting at the bottom of the cookie, apply gentle pressure to the pastry bag and drizzle lines of chocolate back and forth over the cookie, moving up as the chocolate flows. Allow chocolate to set before eating or packaging.
To make polka-dot Valentine hearts, color the remaining chocolate with pink food coloring to the desired shade of pink. Transfer to a disposable pastry bag, twist the end closed, and using scissors, snip a very small opening in the tip. Hold the pastry bag perpendicular to the cookie and apply gentle pressure to pipe a dot of chocolate. Release the pressure on the bag until the flow stops, and continue over the surface of the cookie, piping different sized dots, if desired. Gently tap the cookie to settle the chocolate and allow to set before eating or packaging.
Sift together flour, baking powder, and salt. Set aside. Place butter and sugar in large bowl of electric stand mixer and beat until light in color. Add egg and milk and beat to combine. Put mixer on low speed, gradually add flour, and beat until mixture pulls away from the side of the bowl. Divide the dough in half, wrap in waxed paper, and refrigerate for 2 hours.
Preheat oven to 375 degrees F.
Sprinkle surface where you will roll out dough with powdered sugar. Remove 1 wrapped pack of dough from refrigerator at a time, sprinkle rolling pin with powdered sugar, and roll out dough to 1/4-inch thick. Move the dough around and check underneath frequently to make sure it is not sticking. If dough has warmed during rolling, place cold cookie sheet on top for 10 minutes to chill. Cut into desired shape, place at least 1-inch apart on greased baking sheet, parchment, or silicone baking mat, and bake for 7 to 9 minutes or until cookies are just beginning to turn brown around the edges, rotating cookie sheet halfway through baking time. Let sit on baking sheet for 2 minutes after removal from oven and then move to complete cooling on wire rack. Serve as is or ice as desired. Store in airtight container for up to 1 week.
Recipe courtesy of Alton Brown
If gel paste food colorings are not available, add liquid food coloring until you achieve desired color. For pink, simply use a little red.