Melt the margarine or butter in a large saucepan over low heat. Add the marshmallows and stir until completely melted. Remove from heat.
Mix in the crisped rice cereal. Stir until well coated.
Spread the mixture using a buttered spatula or waxed paper evenly into an 11×17-inch rimmed baking sheet coated with cooking spray. Cut the treats into heart shapes with a 2- 3-inch cookie cutter (enjoy the scraps!) when cool.
Melt the candy melts or white chocolate chips according the package directions. Stir in a few drops of food coloring, if you’d like. Dip the edges of the treats into the candy and decorate with sprinkles. Allow the candy to cool and set before serving.
Best if served the same day.