Line a 9x13 baking dish with foil and spray with nonstick cooking spray.
Heat the 3 tablespoons of butter and 10 oz of mini marshmallows in a large saucepan or dutch oven, stirring occasionally.
Once the marshmallows are 3/4 melted, pour in the 6 cups of Rice Krispie cereal. Gently fold the cereal into the melted marshmallows and pour the Rice Krispie treats into the prepared baking dish and evenly press into the pan and set aside.
Combine the powdered sugar, 1/3 cup melted butter and vanilla extract and a tablespoon of milk at a time. Once the frosting has reached your desired consistency, add in a few drops of pink food coloring and stir to combine.
Attach the small round frosting tip to the disposable piping bag and fill with frosting.
Use the Heart cookie cutter to cut the Rice Krispie treats as close together as possible getting an many as you can.
Take one Rice Krispie heart at a time and place one toothpick on each side so it looks like an arrow coming out from each side.
Stick one gummy heart candy on one toothpick.
Take a second heart and use the kitchen scissors to snip a triangle out of the top. Place this heart on the other toothpick
Gently squeeze the frosting out onto the heart in a back and forth motion.
Sprinkle with Valentine sprinkles
Repeat with all the Rice Krispie hearts.
Spray the spoon with cooking spray before using to stir the melted marshmallows into the cereal.
Use wax paper to press the mixture into the pan (so it doesn’t stick to your hands) or a buttered spatula.