In a large saucepan, melt the butter. Add the marshmallows and stir continuously until completely melted and smooth. Add the vanilla and mix until combined. Remove from heat.
Add in the Rice Krispies and stir until they are all covered in the marshmallow mixture.
Place parchment paper in a rectangular mold, and add in the rice krispie mixture. With a spatula, spread evenly throughout the mold until it's about 1 inch thick.
Grease your heart molds and cut out the first round of hearts. With the rest of the mixture, reshape a square or rectangle, and repeat until you have cut out all the hearts. Place on a large sheet of wax paper.
Let the hearts harden for about 20 minutes.
Prepare the chocolate by adding the white chocolate into a small heat safe bowl, the dark chocolate to another and the candy melts to another bowl. Add 1 teaspoon of coconut oil to the white and dark chocolate. Melt one bowl at a time in the microwave for 20 second intervals until fully melted.
Take a heart and dip the side or the top into the melted chocolate. If you like you can use a spoon to spread chocolate on the top of the hearts. Another option is to use a ziploc bag as a piping bag with a tiny hole cut in one edge to create thin lines. Place the hearts on wax paper and add the sprinkles. Let the hearts set completely before serving.
Enjoy!
Notes
For the chocolate, I suggest to use coconut oil if you want to thin it a little and the coating more even. For example with the white chocolate, if you want a whiter, thicker coat, skip the coconut oil.