01 -
Heat the oven to 350 F. Line a rimmed 13x18-inch sheet pan with parchment and lightly spray it. Beat the cake mix, eggs, milk, oil, sour cream, vanilla, and food coloring until smooth. Spread in the pan and bake for 18-22 minutes, until the center springs back and a toothpick comes out clean.
02 -
Cool the cake completely in the pan. Chill for 20 minutes if it feels delicate, then use a 2 1/2 to 3-inch heart cutter to cut about 14 hearts. Carefully split each heart horizontally with a small serrated knife.
03 -
Beat the cream cheese and butter until smooth. Add powdered sugar, vanilla, and salt, then beat until fluffy. Mix in the marshmallow creme until the filling is light and spreadable.
04 -
Spread or pipe about 1 tablespoon filling on the bottom half of each heart. Add the top halves and press gently so the filling reaches the edges without squeezing out.
05 -
Place the filled cakes on a parchment-lined tray and refrigerate for 30-45 minutes, or freeze for 10-15 minutes, until firm enough to dip without sliding.
06 -
Melt the pink candy melts with shortening in short microwave bursts, stirring until smooth. Dip each chilled heart, let the excess drip off, and set on parchment. Spoon coating over any bare spots while it is still warm.
07 -
Melt the white candy melts and drizzle thin lines over each cake. Refrigerate for 15-20 minutes, until the coating is set. Store covered in the refrigerator until serving.