Spray a 9”x13” casserole dish with cooking spray and set aside.
In a large pot melt butter on medium heat. Add the mini marshmallows to the pot and stir frequently until fully melted.
Pour in crispy rice cereal and gently stir until fully incorporated with the melted marshmallows.
Transfer the mixture to the prepared casserole dish. Using a spatula, press the mixture into an even layer in the casserole dish. Allow to cool completely.
Once cooled, transfer the rice krispie treats to a cutting board and use heart-shaped cookie cutters to cut out hearts.
Divide white candy melts to separate bowls (amount will depend on how many colors you want).
Add white candy melts to microwave safe bowl and melt in microwave in 30 second increments stirring in between until creamy and smooth.
Add 1-2 drops of food coloring and stir. If chocolate seizes up, add a drop or two of avocado oil and stir, adding additional drops of oil until desired consistency is achieved.
Dip hearts into melting chocolate or use a butter knife to spread the chocolate evenly on the tops.
To add writing, spoon melting chocolate into a small sandwich bag. Snip off a very small corner and carefully write messages on each heart.
Allow white candy to harden completely before transferring to an airtight container.