Grease a 9x13 baking pan with cooking spray.
Melt the butter in a large sauce pan or Dutch oven over low to medium heat.
Stir the vanilla extract and salt into the butter.
Add the mini marshmallows to the melted butter mixture, stirring until the marshmallows have fully melted.
Remove the mixture from the heat, and partially stir in the Rice Krispies cereal.
Once you’ve partially mixed together the melted marshmallows with the Rice Krispies cereal, stir in the M&M’s candies and finish mixing everything together.
Spread the Rice Krispies treats mixture into a pan.
Immediately sprinkle on Valentine sprinkles, so they'll stick to the warm marshmallow treats.
Cut heart shaped Rice Krispie treats with a heart shaped cookie cutter. Work your way around the edge, then in toward the middle.
And that's it. They're ready to serve and enjoy!