In a large saucepan, melt the butter over low heat.
Add the marshmallows and stir continuously until completely melted and smooth.
Remove from heat and stir in a few drops of pink or red food coloring until evenly colored.
Add the Rice Krispies cereal and gently fold until fully coated.
Transfer the mixture to a parchment-lined surface and gently press it into an even layer.
While still warm, use a heart-shaped cookie cutter to cut out Valentine shapes.
Let cool completely before serving or decorating.
