Preheat the oven to 350° F.
In a medium bowl, combine the butter, sugar, egg yolk, vanilla extract and red food coloring. Beat with an electric mixer on medium-high speed until creamy, at least 1 minute.
In a small bowl, combine the flour, baking powder and salt. Add this to the wet ingredients in two increments, beating in between each addition. Gather the dough into a ball before proceeding.
Lightly flour a surface, and roll out the dough to about 1/4” thick. Lightly flour a heart-shaped cookie cutter, and cut out as many hearts as possible. Move the hearts to a parchment-lined baking sheet. Gather the scraps, and re-roll and cut out more hearts until all of the dough is used up. You should get about 12 cookies. Move all of the hearts onto the baking sheet, leaving 1/4” space between each cookie.
Place the baking sheet in the freezer for 5 minutes.
Bake the cookies for 10-11 minutes until lightly golden brown on the bottoms. Let cool on the baking sheet for 1 minute to firm up, and then move to a cooling rack to cool completely.
To make the chocolate dip, add the white chocolate chips to a small bowl along with 1 teaspoon of oil. Microwave on medium power for 20 seconds. Stir and microwave again in 20 second pulses until the chocolate is almost melted. Stir until it melts all the way.
Repeat the chocolate melting process with the dark chocolate chips.
Dip half of the heart cookies in white chocolate and half in dark chocolate serve. Let the chocolate set before serving the cookies.